Musnad Ahmad 31:365

Zakariya ibn 'Adi narrated to us, he said: 'Ubayd Allah ibn 'Amr informed us, from 'Abd Allah ibn Muhammad ibn 'Aqil, from 'Ata' ibn Yasar, from Abu Sa'id, who said: "The Messenger of Allah, peace and blessings of Allah be upon him, would break his fast on the day of Fitr before he went out, and he would not pray before the prayer [of 'Eid]. Then, when he finished his prayer, he would pray two rak'ahs."