Does God approve of slavery? Whey doesn't the Bible abolish slavery?
These are important questions! A few things that would be helpful to recognize:
The ancient Hebrew society was very different than our own! Understanding their context and culture...and that of the world around them, will prove very helpful (but requires quite a bit of work!)
Slavery in the Bible is not analogous to slavery in American history; there were a number of key differences. In addition, the best translation of the Hebrew word is arguably NOT 'slave'.
The Old Testament law regulated a broken and sinful society; it's purpose was not to legislate a perfect and sinless society (which is impossible).
The evidence is that there is not a single movement to abolish slavery throughout history that was not motivated by the Biblical Christian worldview.