It is not uncommon to find atheists attacking the morality of the Bible on the subject of slavery, and in so doing, seeking to undermine the very foundations of the Christian faith. They observe—correctly, I might add—that the Bible never issues an outright condemnation of slave-holding, but only seeks to regulate its practice, thus seeming to give it tacit approval. There are numerous provisions in the law, for instance, governing the acquisition, sale, and treatment of slaves (e.g. Ex. 20:8-11, 17; 21:1-6; Lev. 25:39-46; Deut. 15: 12-18; etc.), but nowhere do we find an absolute prohibition stating, “You shall not be a slave-holder.” Neither do we find such an interdiction in Jesus’ teaching, even though he must have interacted with many slaves and slave-holders alike during the course of his ministry, and both figure prominently in his parables (Matt. 13:24-30; 18:21-35; 21:33-41; etc.). Nor do we find a command in any of Paul’s letters requiring masters to release their slaves, but only admonitions to treat them well (Eph. 6:5-9; Col. 3:22-4:1; 1 Tim. 6:1-4). We even find him sending a runaway slave back to his master (Phile. vv. 8-22).
So what are we to make of these things? Atheist Sam Harris says that slavery is perhaps the easiest of all moral questions, and that the Bible gets it wrong. And of course if the Bible gets something this easy so wrong, then its teaching on other matters is also suspect. Harris seeks to claim the moral high ground, which is rather an odd thing for an atheist to do. In a world where God does not exist, there can be no such thing as moral high ground, or low ground for that matter. In a world without God, there is only a vast moral flatland, where no behavior is morally superior to another. Morality is a word signifying nothing. If God does not exist, human beings are, to quote Bertrand Russell, nothing more than “accidental collocations of atoms.” And what does it matter really if one accidental collocation of atoms should happen to capture and enslave another? The most an atheist can say about it is, “I don’t like it.” What he cannot say is, “It is wrong.” He can state his preference if he wishes; but his worldview does not permit him to make a moral judgment.
What is the Bible’s stance on slavery? We will address the subject in the following order:
What is a slave?
To alleviate the effects of poverty
To punish criminal behavior
To punish and restrain enemy nations
Treatment of slaves
Summary and Conclusion
What is a Slave?
The Hebrew word for slave is derived from a verb meaning to work. Thus, a slave is a worker, and he is acquired for this purpose. However, under Biblical law, a slave differs from an ordinary hired worker in that the slave becomes a member of his master’s household (cf. Gen. 14:14; 15:2-3; 17:12-13, 23, 27; 24:2; Lev. 22:11; etc.).
Biblical law neither approves of nor condemns slavery per se. Some forms are permitted, others forbidden. The distinguishing feature between them lies in the manner in which a person is reduced to the status of slave. Unlawful enslavement takes place when someone is forced into it against his will and without deserving it for crimes committed. Thus, the Bible in no uncertain terms condemns the practice of kidnapping for the purpose of turning free men into slaves.
Whoever steals a man and sells him, and anyone found in possession of him, shall be put to death (Ex. ).
The severity of the punishment is indicative of how grievous this sin is in the eyes of God. He reckons “man-stealing” a crime punishable by death. Surprisingly, Harris fails to mention this passage. Paul alludes to it, however, in his first letter to Timothy.
Now we know that the law is good, if one uses it lawfully, understanding this, that the law is not laid down for the just but for the lawless and disobedient, for the ungodly and sinners, for the unholy and profane, for those who strike their fathers and mothers, for murderers, the sexually immoral, men who practice homosexuality, enslavers [lit., man-stealers] (1 Tim 1:8-10)
These prohibitions against man-stealing apply to private individuals as well as to criminal gangs, and even to rogue nations that make war for the purpose of capturing free men and making them slaves.
Being kidnapped was not the only means by which someone in Israel might have become a slave. Biblical law, in fact, recognizes three morally justified scenarios in which one might have been reduced to this unfortunate status.
Alleviation of Poverty
The first of these was for the purpose of alleviating the effects of poverty. If a man had become so poor that he was unable to provide for himself, or was unable to repay a loan, he might sell himself as a slave to a wealthy neighbor (Lev. 25:39; Deut. 15:12). In this arrangement, the buyer assumed the responsibility of providing for the impoverished man and his family. In return, the man worked for the buyer in order to earn his keep. At the end of six years (Ex. 21:2; Deut. 15:12), or in the year of Jubilee (Lev. 25:40)—whichever came first—he was to be set free. During his time of servitude, he was to be treated mildly, like a hired servant, not harshly, as if held against his will. This was, after all, a voluntary arrangement (though once entered, both parties were legally bound to fulfill the terms of the agreement). This arrangement might be thought of as a privately run, work-based welfare program, regulated by divine law. When the man’s term of service came to an end, the law required that his master supply him generously with the means to begin life anew.
When you let him go free from you, you shall not let him go empty-handed. You shall furnish him liberally out of your flock, out of your threshing floor, and out of your winepress. As the Lord your God has blessed you, you shall give to him (Deut. 15:13-14)
This was a compassionate arrangement that was mutually beneficial to master and slave alike. The master had the service of a grateful man whom he rescued from poverty; the poor man’s needs were met, and he would presumably learn the skills and develop the character traits necessary to live successfully as a free man. If he preferred, however, he might choose to continue as a slave in his master’s household.
But if he says to you, “I will not go out from you,” because he loves you and your household, since he is well-off with you, then you shall take an awl, and put it through his ear into the door, and he shall be your slave forever (Deut. 15:16-17)
Most people, I should think, would be glad to regain their freedom once they had recovered from poverty; but it is conceivable, given their kindly treatment, that some might prefer the security of slavery to the responsibilities of freedom.
Punishment of Criminal Behavior
The same arrangement might be made in the case of a man who came by his debt through criminal behavior. It is said of a thief, “He shall surely pay [i.e., pay back what he had stolen, plus an additional amount as a penalty]. If he has nothing, then he shall be sold for his theft” (Ex. 22:3). The same principles applied in cases with other forms of criminal or negligent behavior resulting in financial loss. Biblical law regards the wrongdoer as having a moral and legal obligation to compensate the victim (e.g., Ex. 21:33-34; 22:6). If he did not have the means to do so, he might be sold into slavery, with his purchase price going to his victim.
To Punish and Restrain Enemy Nations
Another scenario in which slavery was recognized under Biblical law involves captives taken in war. The question of what to do with prisoners of war has often proved to be a vexing one. Releasing them, even after a formal end to hostilities, involves the risk that they will take up arms again. In order to avoid this, some victors have employed a policy of “no mercy” and have simply killed their captives. Others have chosen to put them to forced labor as state slaves or sell them to foreign nations. Biblical law permitted this (Deut. 20:10-11). This was a more merciful option than killing them, was less risky than releasing them, and could help toward the recovery of some of the costs of war.
In the same way that a man in the Israel might have sold himself as a slave to alleviate the effects of poverty, so he might have sold a son or a daughter (Neh. 5:1-5). The same provisions applied with regard to the time of service (i.e., release in the seventh year) (Deut. 15:12; cf. Jer. 34:8-22). In some cases, however, special provisions were made for a daughter: the arrangement might include a promise of marriage (Ex. 21:7-11). If a man’s poverty was so great that he was unable to provide for his daughter, he might sell her as a slave with a view to becoming her master’s wife. This is what it means when it says that the purchaser “designated her for himself” (Ex. 21:8), i.e., he promised to take her as his wife when she should come of age. Or, instead of designating her for himself, he might designate her for his son (v. 9). Contrary to what some have alleged, there is nothing in the text suggesting that she was sold as a sex-slave for her master. She was most likely charged with the household duties common to daughters. This was, in fact, a form of betrothal. The medieval Jewish scholar, Maimonides says, “A Hebrew handmaid might not be sold but to one who laid himself under obligations to espouse her to himself or to his son, when she was fit to be betrothed.”
A male Hebrew slave was to “go out” after six years of service. Not so the female slave in question (Ex. 21:7b). She entered the arrangement with a promise of marriage. If her master changed his mind and decided not to marry her because “she does not please her master” (v. 8), he was guilty of a breach of faith (v. 8). To send her out as a young single woman with no means of support would have been an act of cruelty. She was to continue to be provided for in her master’s house, and he was to “deal with her as [kindly and affectionately as] with a daughter” (v. 9). I take this to include an effort to find a suitable husband for her. “If he takes another wife [instead of her] to himself [or for his son] he shall not diminish her food, her clothing, or her marital rights” (Ex. 21:10). The Hebrew word for “marital rights” means “dwelling” or “habitation.” Some understand this as a euphemism for sexual relations and suppose that the girl has been living, not as her master’s betrothed, but as his concubine. It is better, however, to take the word in its basic meaning of “dwelling,” and regard her not as a concubine, but a bride in waiting. If her master, however, should decide against marrying her, and take another woman as his wife instead, he must not diminish her food, her clothing, or her living arrangements. He is bound by his original agreement. He may not take what was pledged for her support and give it to another whom he finds more pleasing. 
Unlike Hebrew slaves, who must be released in the seventh year, foreign slaves might be kept in perpetuity and even passed on to one’s heirs. They might be purchased from other nations or from the resident aliens within the borders of Israel (Lev. 25:44-46).
The apparent harshness of this law must be viewed in light of the law as a whole as it regards resident aliens. Like native Israelites, resident aliens could not be enslaved, except as a punishment for crime or in order to pay a debt, and only after a formal conviction in a court of law. On the contrary, strangers were to be treated with kindness and consideration (Lev. 19:33-34). They were to be given access to the gleanings of Israel (Lev. 19:9-10; Deut. 24:19-21). Strict warnings were given against oppressing them (Ex. 22:21; 23:9; Lev. 19:33; cf. Mal. 3:5). They were to be given rest on the Sabbath day (Ex. 20:12; 23:19). They had the same legal standing in court as native Israelites (Deut. 1:16; 24:17-18). They had the same right of asylum in the cities of refuge (Num. 35:15). They were not to be defrauded of their wages (Deut. 24:14-15). They could own Hebrew slaves (Lev. 25:47). And if they had been slaves in a foreign land and had escaped, they were to be given a safe haven in Israel (Deut. 23:15-16). Resident aliens could not hold office (Deut. 17:15); but they could serve as warriors and advisors (2 Sam. 18:2; 23:39). If they were converted from their pagan religion and worshiped the God of Abraham, they were admitted into the full religious privileges of Israel (Ex. 12:43-49; Num. 9:14). Full rights of citizenship, including the right to hold a governing office, could be granted in subsequent generations (Deut. 23:2-8).
What, then, was the rationale for allowing foreigners to be held as slaves in perpetuity? It may have been to encourage such slaves to convert to the worship of Yahweh, and thus be entitled to the terms governing the release of Hebrew slaves (Ex. 21:2; Deut. 15:12).
Treatment of Slaves
Biblically sanctioned slavery did not regard the person but the labor of the slave as the property of the master. This is an important distinction. A slave-owner was not permitted to do whatever he wanted with his slave. It was required that masters allow their slaves to rest on the Sabbath and on other holy days (Ex. 20:8-11; etc.). If a master mistreated a slave so that permanent bodily damage resulted, the slave was to be set free (Ex. -27). If he killed his slave, the slave was to be “avenged” (i.e., the slave-owner was to be executed) (Ex. -21).
Manumission might take place in a variety of ways. As mentioned above, the law imposed a limit on the number of years a Hebrew slave might be required to serve, i.e., six years. At the end of this, he was to be allowed to “go out free, for nothing” (Ex. 21:2; Deut. 15:12). More than this, his master was to send him away laden with livestock, grain, and wine (Deut. 15:14).
A slave was to be released early, however, if the year of Jubilee should arrive before the completion of six years (Lev. 25:39-41). He might be released early, even apart from the year of Jubilee, if he should be redeemed by his relatives (Lev. 25:47-49). He might even prosper sufficiently so as to redeem himself (Lev. 25:49).
In Exodus 21:3-4 the issue of manumission is considered vis-à-vis the slave’s marital status and what should become of his wife and children when he is set free. There were three possible circumstances under which a slave’s manumission might take place: (1) The slave might have been unmarried when he became a slave and continued unmarried throughout his years of service, in which case there was no one else to set free; (2) the slave might have been married when he began his service, in which case his wife was to be released with him; or (3) the slave might have been unmarried when he began to serve, but at some point during his years of service he might have been given a wife by his master. In this case, the wife and any children born to her were to continue in the master’s service, and the man alone was to be set free. This is not to say that they would no longer be married, but that he would be free, and his wife and children would continue to be subject to their master. “This may appear oppressive, but it was an equitable consequence of the possession of property in slaves at all.” The master had a financial investment in the woman, and she would remain a slave under his authority until her newly freed husband could manage to redeem her. Her original purchase price naturally included her potential to bear children, and so the children also remained under the master’s authority until such time as they were redeemed.
Summary and Conclusion
Let us summarize. Under Biblical law, slavery was permitted for the following reasons: (1) as a means of alleviating the effects of poverty, (2) to make restitution for financial losses caused by criminal or negligent behavior, and (3) to punish and restrain enemy nations. In all of these scenarios, the slave-holder had a legal claim upon the fruit of his slave’s labor. Under no circumstances did Biblical law condone capturing or kidnapping free and innocent people in order to make slaves of them. Further, slaves had certain rights and protections that could not be denied to them.
This is slavery as it existed in Israel, regulated by the law of God. And it is altogether different from how slavery was practiced elsewhere in the ancient Near East or in the Greco-Roman world. In these cultures, slaves had little to no legal protection. Not only the labor, but the bodies and souls of men were regarded as the property of their masters, who could do with them whatever they pleased, even kill them, without any legal repercussions. Slavery in Israel, as sanctioned in the Bible, was quite different from this, and quite different, too, from the slavery of the antebellum South, which had a racial component to it that has greatly complicated race relations in the U.S. ever since. To compare the slavery of the Bible, then, with slavery as it has existed elsewhere (and still exists in the Muslim world) is to compare apples and oranges. There are far more differences than similarities.
We should conclude by observing that the Bible clearly favors freedom over slavery. Paul writes to the Corinthians, “Were you a slave when called? Do not be concerned about it. (But if you can gain your freedom, avail yourself of the opportunity.) (1 Cor. 7:21). In other words, “Gain your freedom if can lawfully do so.” A little later he says, “You were bought with a price; do not become slaves of men” (v. 23).
Slavery is by no means a creational ordinance. It is a state of affairs that did not enter the world until the fall of man. Apart from sin, there would never have been a need for it. Under Biblical law it was a corrective or remedial measure.
 Sam Harris, Letter to a Christian Nation (New York, NY: Alfred A. Knopf, 2006), pp. 14-18
 Bertrand Russell, Why I Am NOT a Christian (New York, NY: Simon and Schuster, 1957), p. 107
 See Haim H. Cohn, in The Principles of Jewish Law, edited by Menachem Elon (Jerusalem, Israel: Keter Publishing House, 1975), p. 231
 This is a glaring omission. So is his failure to mention the several other ways (distinguished in Scripture and discussed below), by which someone might have been reduced to slavery. Perhaps we should not be too surprised, however, by these omissions. In reading him, one gets the impression that Harris is not very interested in actually understanding the Scriptures or the real-life situations they address, and even less interested in representing them fairly.
 The pierced ear was a permanent visible sign of his pledge. The procedure had to be done with a priest as a witness in order to guarantee its voluntary nature (Ex. 21:6).
 This invites a comparison with the modern prison system, which is a type of enslavement, but without the work requirement, and thus without the personal and social benefits of restitution to the victim and the character development of the thief through productive labor and the daily oversight of a successful man. Cf. Eph. 4:28, “Let the thief no longer steal, but rather let him labor, doing honest work with his own hands, so that he may have something to share with anyone in need.”
 The problem of what to do with captives of war has been one of the dilemmas that the U.S. has faced with the prisoners held at Guantanamo Bay. The rationale for keeping them locked up is to prevent them from continuing their fight against the West either in terrorist acts or on the battlefield. In fact, a good number of these prisoners who have been released have reentered the fight. According to a National Intelligence summary report, it is estimated that nearly thirty percent of those released have done so: http://www.dni.gov/files/documents/Newsroom/Reports%20and%20Pubs/GTMO.pdf (Accessed March 15, 2015)
 Sam Harris, p. 15
 Cited in George Bush, Commentary on Exodus (Grand Rapids, MI: Kregel Publications,  1993), p. 310
 Although as noted above, she might have entered this service without a promised marriage, in which case she was released after six years of service (Deut. 15:12).
 See the discussions in Umberto Moshe David Cassuto, A Commentary on Exodus (Skokie, IL: Varda Books, 2005), p. 268-269; and Shalom M. Paul, Studies in the Book of the Covenant in Light of Cuneiform and Biblical Law (Eugene, OR: Wipf & Stock Publishers, 2006), pp. 59-61
 This serves to show how mildly slaves were to be treated under Biblical law that they could conceivably purchase their own freedom.
 C.F. Keil, Commentary on the Old Testament (Peabody, MA: Hendrickson Publishers, 1989), vol. 1, p. 130
 Here and elsewhere the law recognizes the financial investment a master has tied up in his slaves and requires that he be duly compensated for their emancipation, either by the slave’s labor over a set period of time, or by a payment of money. This was how Great Britain finally abolished slavery throughout its realms; the British government compensated slave owners. This was an equitable solution to the problem, and one consistent with Biblical law. Similar plans were put forward in the United States but failed to garner enough support to be implemented. It took, instead, rivers of blood to put an end to it.
 Not commanded, but permitted
 These claims are often handled today by a court-ordered garnishing of wages.
 This is not to say that Israel always observed the law (see Jer. 34:8-22)