Sayyiduna Abu Dharr (may Allah be pleased with him) said: I asked the Messenger of Allah (peace and blessings be upon him): Which deed is best? He (peace and blessings be upon him) said: "Faith in Allah and striving (jihad) in the path of Allah." I asked: Which slaves are best (to free)? He (peace and blessings be upon him) said: "Those that are most expensive and most prized by their owners." He (Sayyiduna Abu Dharr, may Allah be pleased with him) said: (I said:) What if I cannot do that? He (peace and blessings be upon him) said: "Help a craftsman, or teach someone who is unskilled." He said: (I asked:) What if I cannot do (even) that? He (peace and blessings be upon him) said: "Spare people from (your) evil, for that too is a charity that you give."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العتق / 21314