“Our Prophet (peace be upon him) never approved of slavery. He once purchased the life of a slave who came to him, liberating him from his master!”
Here is the real story on which that excerpt (of Muhammad ‘liberating a slave’) is based:
Muhammad actually “purchased” the slave by trading two black slaves, which is hardly a shining example of emancipation. Not only that, it establishes the fact that Muhammad owned and traded African slaves. As a wealthy businessman, he certainly could have liberated all three slaves, but chose instead to sell the two Africans into an uncertain future.
It is also obvious from the passage that Muhammad felt he had been conned into liberating the slave who had come to him, since he was not told of his status as a slave. Because, of this, Muhammad decided that he would not be duped again. In the future, he would always ask first about whether a man was free or not before deciding whether to accept allegiance.
There is also no record of Muhammad “liberating” slaves captured in battle, unless there was something to be personally gained from it. In fact, he made slaves out of those who were previously free people, particularly if they were women and children. Sometimes he used families as leverage to force their men into accepting Islam:
Captured women were passed out like party favors to his men, some of whom were then passed along to others (just like the Islamic State does with Yazidi women). This passage tells of Muhammad giving women as sex slaves to the three men who would become his successors, the future caliphs Umar, Uthman and Ali:
Allah gave Muslim men a divine mandate to keep as many sex slaves as they wished (Quran 4:24,33:52…). Contemporary apologists sometimes pretend that this applies only to women captured in battle (see also Myth: Muhammad Would Never Approve of Rape), but the same privilege is granted to believing men in 70:30, a passage “revealed” to the Muslims in Mecca, when there had been no battles.
Much could be written about Muhammad’s prolific and well-documented relationship with slaves, but one of the most insightful examples comes from this hadith (which is repeated elsewhere):
According to this hadith, the very pulpit that Muhammad preached Islam from was constructed from slave labor on his command! Now does this sound like Muhammad had a problem with slavery?