Galatians 3:26So in Christ Jesus you are all children of God through faith, 27for all of you who were baptized into Christ have clothed yourselves with Christ. 28There is neither Jew nor Gentile, neither slave nor free, nor is there male and female, for you are all one in Christ Jesus. 29If you belong to Christ, then you are Abraham’s seed, and heirs according to the promise.
This is one of the seminal passages that describes the work of Christ in separating out from the nations a people called by his name. Yes there are passages in the NT telling Chrisitians who are slaves to accept their Earthly lot just as there is a passage telling a Christian slave owner just how he was to treat a returning slave who also was a Christian(”as a brother”).
Yet the progressive drive of the Spirit of Grace thru-out time was the creating of a people in which there would be no slavery,no worldly difference in tribes, castes, or royalty only the unity between men thru Jesus Christ. Galatians chapter 3 lays out the work of the Mosaic law in convincing men of their absolute failure before God in not living as they ought, yet also points out the law as being the incubator of the way of Christ.
That Christianity has been falsely framed in support of slavery is the work of devils. The work of the Spirit has actually been instrumental in many slaves being freed by their newly enlightened masters thru-out history....in overtly public ways or in ways that never made the history books.
Yet slavery isn’t forbidden in the Bible, not considered immoral.