Not a single word anywhere in the Bible saying that owning slaves is a moral evil. No commandment, "Thou shalt not take any person to be property."
Kind of like the US constitution prior to the civil war. On the other hand there are no statements that slavery is good. It's routinely considered a bad thing throughout the Bible.
If you're looking for statements of modern sensibilities in the Bible you're not going to find them. It's a 2000 year old book written in a very different time.
The books of Galatians and Philemon contain pleas to free slaves but you'd have to do a lot of research into the early Christian writers to see what they really thought about where slavery was going. The real crime is that slavery still exists today. However, it's rare in the Christian parts of the world.