Musnad Ahmad 16:7

Muhammad ibn Bakr narrated to us, Thabit ibn 'Umarah narrated to us, Rabi'ah ibn Shayban narrated to us, that he said to al-Hasan ibn 'Ali, may Allah be pleased with them: "What do you remember from the Messenger of Allah, may Allah bless him and grant him peace?" He said: "He took me into the charity room, and I took a date from it and put it in my mouth. The Messenger of Allah, may Allah bless him and grant him peace, said: 'Cast it out, for it is not lawful for the Messenger of Allah, may Allah bless him and grant him peace, nor for anyone from his household.'"