Abu Hurayrah (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "Whoever manumits a Muslim, Allah will save from Hell each organ of his body for each organ of him (i.e. of the manumitted person).''
In this Hadīth, Abu Hurayrah (may Allah be pleased with him) says that the Prophet (may Allah's peace and blessings be upon him) explained the virtue of emancipating people from slavery. It is one of the greatest acts of worship that draws one closer to Allah and frees him from Hell. If one manumits slaves for Allah's sake, his reward is that Allah will set him free from Hell. Since the reward is of the same kind of the deed, the manumitter is rewarded by being manumitted from Hell. This immense reward is – and Allah knows best – because a slave has no control over himself, for he is subject to someone else who controls him just as he controls a riding animal. So, emancipating him is like taking him out of nonexistence into existence. He is freed from the harm of slavery and is given control over himself. He can thus implement the religious rulings that apply to him and make his own decisions according to his free will and choice within the limits of Shariah.