Musnad Ahmad 30:2600

Waki’ narrated to us, Shu’bah narrated to us, from Muhammad ibn Ziyad, from Abu Hurayrah, and ‘Abd al-Rahman, from Shu’bah, from Muhammad ibn Ziyad, who said: I heard Abu Hurayrah—the meaning being—that the Prophet, peace and blessings of Allah be upon him, saw al-Hasan ibn ‘Ali take a date from the dates of the charity, and he chewed it in his mouth. The Prophet, peace and blessings of Allah be upon him, said: "Kakh, kakh! For indeed, charity is not lawful for us."