Muslims inherited a great number if slaves from the empires they conquered. The most responsible political course of action was to introduce gradual manumission

Muslims inherited a great number if slaves from the empires they conquered. The most responsible political course of action was to introduce gradual manumission with incentives that would benefit the people of the Caliphate. So yes, they did free slaves. It wasn't some fairy tale day 1 everyone is free now, let society burn in disorder, do whatever you want, but it was the correct thing to do.