Musnad Ahmad 30:640

'Abd al-Razzaq narrated to us, Ma'mar informed us, Muhammad ibn Ziyad informed me that he heard Abu Hurayrah saying: We were with the Messenger of Allah, may Allah bless him and grant him peace, while he was distributing dates from the dates of charity, and al-Hasan ibn 'Ali was in his lap. When he finished, the Prophet, may Allah bless him and grant him peace, carried him on his shoulder. His saliva flowed onto the Prophet, may Allah bless him and grant him peace. The Prophet, may Allah bless him and grant him peace, raised his head, and behold, there was a date in his mouth. The Prophet, may Allah bless him and grant him peace, inserted his hand and pulled it out from him. Then he said: "Do you not know that charity is not lawful for the family of Muhammad?"