Is it obligatory for a slave who performed Hajj and then was emancipated to repeat Hajj, and what is the wisdom behind that if it becomes obligatory for him?

Scholars have differed regarding the sufficiency of Hajj for a slave if he performs it before being manumitted. The majority of them hold that it is not sufficient, while Abu Muhammad Ibn Hazm and some other scholars maintain that Hajj is obligatory for him, valid from him, and sufficient for him.

The correct view is that of the majority, which states that if a slave performs Hajj, his Hajj is valid, but it does not suffice for his obligatory Hajj (Hajj al-Islam), and that Hajj is not obligatory for him while in slavery. This is based on the Prophet's (peace be upon him) saying: "Any slave who performs Hajj and is then manumitted must perform another Hajj." This Hadith is considered sound (sahih) and مرفوع (traced back to the Prophet) by many Hadith scholars.

The difference between Hajj and other acts of worship is that Hajj is not obligatory for a slave while in slavery, similar to a child, whereas prayer and fasting are obligatory for him. For this reason, he is not required to repeat them if he is manumitted.