Why does God allow slavery in the Old Testament?

The reason the Bible talks about slavery is that slavery was a very common
phenomenon in both Old Testament and New Testament times. It is only
natural that the topic would come up, both from a legal stand point and
simply as a common part of the history recorded in both Testaments.

Your second question is more challenging. It would appear from the Old
Testament that God did not specifically condemn slavery. That may seem odd
to us, as slavery is such a clear violation of basic human justice. It is
not as if the Bible ever encourages slavery. You will not find a single
passage of scripture which in any way whatsoever encourages any follower
of God to own slaves. However, in the Old Covenant, God did allow for
slavery. God allowed a number of practices under the Old Covenant which he
nevertheless did not want his people to do. God made concessions under the
Old Covenant for divorce, although he never wanted divorce to happen.
“Moses (and presumably, therefore God) permitted you to divorce because
your hearts were hard. But it was not this way from the beginning.”
(Matthew 19:8) I would assume God’s attitude toward slavery in the Old
Testament would fall under the same category. Slavery was a fact of life
in the ancient world. Victory in battle produced slaves. Period.
Therefore, for his own reasons, God chose to regulate the cruelty of
slavery rather than to ban it outright for the Jews under the Law of
Moses. He commanded that slaves be set free automatically after a certain
amount of time. He forbade excessive cruelty to slaves. He commanded that
they be allowed a certain level of access to the ceremonies of Judaism and
so forth. See Deuteronomy 23:15, Leviticus 25:14 as examples.

What about the New Testament? Slavery is neither specifically allowed not
specifically condemned in the New Testament. At first, knowing Jesus’
teaching, this may seem a bit surprising. Clearly Jesus would never own
slaves! Nevertheless, slavery was a massive institution under Greek/Roman
civilization. As many as half of all people were slaves. If Jesus had
declared all slaves free under the New Covenant, it would have brought
massive and unnecessary persecution down on the early church. Perhaps this
is why God chose not to specifically condemn slavery. Paul encouraged
Philemon to free his slave Onesimus. Yet, in general, he encouraged new
disciples to be willing to stay in the situation they were in when
converted. As far as God is concerned, whether one is a slave or free here
on earth is not the main issue. The chief concern is whether one is a
slave to sin. God, through Paul, encouraged Christian slaves to be the
best possible slaves, yet to seek freedom if they could. He did not incite
slaves to revolt from their masters. I am sure that a slave who was owned
by a disciple would have lived under exceedingly good and fair conditions,
if he or she was not freed outright.

It is worth bearing in mind that in the end, it was Christianity and the
teachings of the Bible which led to the worldwide ban on slavery. Although
it is true that due to the extreme level of slavery in the time of the New
Testament, God chose not to ban the practice outright, history tells us
that it was the teachings of Jesus Christ which caused the downfall of the
cruelest institution mankind ever invented.

John Oakes, PhD