https://www.chabad.org/parshah/article_cdo/aid/1750159/jewish/The-Slow-End-of-Slavery.htm
Slavery was abolished in the United States only after a civil war, and there were those who cited the Bible in defence of slavery. As Abraham Lincoln put it in his second Inaugural: “Both read the same Bible and pray to the same G‑d, and each invokes His aid against the other. It may seem strange that any men should dare to ask a just G‑d’s assistance in wringing their bread from the sweat of other men’s faces, but let us judge not, that we be not judged.”
Yet slavery was abolished in the United States, not least because of the affirmation in the Declaration of Independence that “all men are created equal,” and are endowed by their Creator with inalienable rights, among them “life, liberty and the pursuit of happiness.” Jefferson, who wrote those words, was himself a slaveowner. Yet such is the latent power of ideals that eventually people see that by insisting on their right to freedom and dignity while denying it to others, they are living a contradiction. That is when change takes place, and it takes time.
If history tells us anything, it is that G‑d has patience, though it is often sorely tried. He wanted slavery abolished, but He wanted it to be done by free human beings coming to see of their own accord the evil it is and the evil it does. The G‑d of history, who taught us to study history, had faith that eventually we would learn the lesson of history: that freedom is indivisible. We must grant freedom to others if we truly seek it for ourselves.