Musnad Ahmad 32:328

Haram ibn 'Umarah narrated to us, he said: Marji' ibn Raja' narrated to me, from 'Ubayd Allah ibn Abi Bakr ibn Anas, from Anas ibn Malik, who said: "When the day of Fitr arrived, the Messenger of Allah (peace and blessings of Allah be upon him) would not go out until he had eaten some dates, which he would eat in odd numbers."