Musnad Ahmad 495:5

Ya'qub and Sa'd narrated to us, they said: My father narrated to us, from Salih, from al-Zuhri, from 'Ubayd Allah ibn 'Abd Allah ibn al-Harith ibn Nawfal ibn al-Harith ibn 'Abd al-Muttalib, that he informed him that 'Abd al-Muttalib ibn Rabi'ah ibn al-Harith ibn 'Abd al-Muttalib informed him: That Rabi'ah ibn al-Harith and al-'Abbas ibn 'Abd al-Muttalib gathered and said: "By Allah, if we sent these two boys"—referring to me and al-Fadl ibn 'Abbas—"to the Messenger of Allah, may Allah bless him and grant him peace, and he appointed them over these charities, they would perform what the people perform, and they would obtain what the people obtain of benefit." While they were discussing that, 'Ali ibn Abi Talib came and said: "What do you two want?" They informed him of what they intended. He said: "Do not do it, for by Allah, he will not do it." He [the narrator] said: "Why do you do this? This is nothing from you but jealousy toward us. You have accompanied the Messenger of Allah, may Allah bless him and grant him peace, and attained his kinship, and we have not been jealous of you for that." He said: "I am Abu Hasan, send them." Then he lay down. He said: "When he prayed the Dhuhr prayer, we preceded him to the chamber and stood by it until he passed by us. He took our hands, then said: 'Bring out what you are concealing.' He entered and we entered with him, and he was at that time in the house of Zaynab bint Jahsh." He said: "We spoke to him and said: 'O Messenger of Allah, we came to you so that you would appoint us over these charities, so we may obtain what the people obtain of benefit, and we will perform for you what the people perform.' The Messenger of Allah, may Allah bless him and grant him peace, remained silent and raised his head toward the ceiling of the house until we wanted to speak to him." He said: "Zaynab signaled to us from behind her veil as if she were forbidding us from speaking to him. He turned and said: 'Verily, charity is not appropriate for Muhammad nor for the family of Muhammad; it is only the filth of the people. Call for me Mahmiyah ibn Jaz'—who was in charge of the tithe—and Abu Sufyan ibn al-Harith.'" They came, and he said to Mahmiyah: "Pay them from the one-fifth."