Sahih Muslim Book 5, Hadith Number 2348.

Chapter : Accepting of gift by the Holy Prophet (may peace be upon him) and refusing the Sadaqa.

Rabi’a b. Harith b. ‘Abd al-Muttalib and Abbas b. ‘Abd al-Muttalib said to Abd al-Muttalib b. Rabi’a and Fadl b. Ibn Abbas: Go to the Messenger of Allah (may peace be upon him), and the rest of the Hadith is the same (but with this addition): “‘Ali spread his cloak and then lay down on it and said: I am the father of Hasan, and I am the chief. By Allah, I would not move from my place till your sons come back to you with the reply to that for which you sent them to the Messenger of Allah (may peace be upon him). And he then also said: Verily these sadaqat are the impurities of people, and they are not permissible for Muhammad (may peace be upon him), and for the family of Muhammad. And he also said: The Messenger of Allah (may peace be upon him) also said to me: Call Mahmiya b. Jaz’, and he was person from Banu Asad and the Messenger of Allah (may peace be upon him) had appointed him as a collector of khums.