Musnad Ahmad 30:3043

Waki’ narrated to us, Shu’bah narrated to us, from Muhammad ibn Ziyad, from Abu Hurairah, that the Prophet, may Allah bless him and grant him peace, saw Al-Hasan ibn Ali take a date from the dates of the charity, and he chewed it in his mouth. The Prophet, may Allah bless him and grant him peace, said to him: "Kakh, kakh! Indeed, charity is not lawful for us."