Musnad Ahmad 30:1917

'Affan narrated to us, Khalifah ibn Ghalib al-Laythi narrated to us, he said: Sa'id ibn Abi Sa'id al-Maqburi narrated to us, from his father, from Abu Hurayrah, that a man came to the Messenger of Allah, peace and blessings of Allah be upon him, while he was with him, and asked him, saying: "O Prophet of Allah, which deeds are best?" He said: "Faith in Allah, and Jihad in the way of Allah." He said: "If I am not able to do that?" He said: "Then which of the necks [slaves] is greatest in reward?" He said: "The most expensive of them in price, and the most precious of them to their owners." He said: "If I am not able?" He said: "Help one who is lost, or do work for one who is clumsy." He said: "If I am not able to do that?" He said: "Then restrain yourself from evil, for it is a good charity that you bestow upon yourself."