It is narrated from Sayyiduna Abu Dharr (may Allah be pleased with him) that a man came to the Prophet (peace and blessings be upon him) and said: O Messenger of Allah! Which deed is best? He (peace and blessings be upon him) said: "Faith in Allah and striving (jihad) in His path." He said: Which slave is best to free? He (peace and blessings be upon him) said: "The one with the highest price and the most precious to its owners." He said: And if I am not able to? He (peace and blessings be upon him) said: "Help a weak person, or do work for someone who is unskilled." He said: And if I cannot do even that? Then he (peace and blessings be upon him) said: "Keep people safe from your evil; that too is a charity that you give to yourself."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الوصايا / 12595
Sayyiduna Abu Hurayrah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Whoever frees a believing slave, Allah Almighty will free every limb of his from Hell in return for a limb of that slave. He frees a hand for a hand, a foot for a foot and private parts for private parts." Ali bin Husayn (may Allah have mercy on him) said to the narrator: Did you hear this from Sayyiduna Abu Hurayrah (may Allah be pleased with him)? He said: Yes. Ali (may Allah have mercy on him) said: Call Mutarrif for me, and he was one of his most able slaves. When he stood before him, he said: You are free for the pleasure of Allah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الوصايا / 12596
It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Whoever frees a believing slave, Allah will free every limb of his from the Fire in return for a limb of that slave, even his private parts in return for the private parts (of the freed slave)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الوصايا / 12597