"And such of your slaves as seek a writing (of emancipation), write it for them if ye are aware of aught of good in them, and bestow
upon them of the wealth of Allah which He hath bestowed upon you. Force not your slave-girls to whoredom."
Well, I guess this is about as good as it gets in the Quran. Allah encourages you to set your slaves free if they are good enough.
And don't pimp out your slave-girls (concubines). 24:33
