Abu Dawud Book 3, Hadith Number 1646.

Narated By AbuRafi’ : The Prophet (PBUH) sent a man of the Banu Makhzum to collect sadaqah. He said to AbuRafi’: Accompany me so that you may get some of it. He said: (I cannot take it) until I go to the Prophet (PBUH) and ask him. Then he went to him and asked him. He said: The sadaqah is not lawful for us, and the client of a people is treated as one of them.