Musnad Ahmad 17:2

Waki’ informed us, Thabit ibn ‘Umarah narrated to us, from Rabi’ah ibn Shayban, who said: I said to al-Husayn ibn ‘Ali, may Allah be pleased with him: "What do you remember from the Messenger of Allah, may Allah bless him and grant him peace?" He said: "I climbed into a room and took a date, then I chewed it in my mouth. The Prophet, may Allah bless him and grant him peace, said: 'Cast it away, for charity is not lawful for us.'"