Sahih Muslim Book 19, Hadith Number 4350.

Chapter : Fai’ (property taken from the enemy without a formal war).

The same hadith has been narrated by a different chain of transmitters with a slight variation in wording: ‘Umar b. al-Khattab sent for me and said: Some families from your tribe have come to me (then follows the foregoing hadith) by Malik with the difference that the Messenger of Allah (may peace be upon him) would spend on his family for a year. And sometimes Ma’mar said: He would retain sustenance for his family for a year, and what was left of that he spent in the cause of Allah, the Majestic and Exalted.