Sahih Bukhari

Narrated Abu Dhar:I asked the Prophet, ""What is the best deed?"" He replied, ""To believe in Allah and to fight for His Cause."" I then asked, ""What is the best kind of manumission (of slaves)?"" He replied, ""The manumission of the most expensive slave and the most beloved by his master."" I said, ""If I cannot afford to do that?"" He said, ""Help the weak or do good for a person who cannot work for himself."" I said, ""If I cannot do that?"" He said, ""Refrain from harming others for this will be regarded as a charitable deed for your own good