Musnad Ahmad 315:1

'Abd al-Razzaq narrated to us, Sufyan narrated to us, from 'Ata' ibn al-Sa'ib, who said: Umm Kulthum bint 'Ali narrated to me. She said: I brought her a charity that he had ordered. She said: "Beware, our young ones, for Maymun—or Mihran—the freed slave of the Prophet, may Allah bless him and grant him peace, informed me that he passed by the Prophet, may Allah bless him and grant him peace, and he said to him: 'O Maymun—or O Mihran—we are a household that has been forbidden from charity, and our freed slaves are from among ourselves, and we do not eat charity.'"