Musnad Ahmad 1017:107

Harami ibn 'Umarah narrated to us, Thawab ibn 'Utbah al-Mahri narrated to me, 'Abdullah ibn Buraydah narrated to me, from his father: "That the Messenger of Allah, peace and blessings of Allah be upon him, when it was the day of al-Fitr, he would not go out until he had eaten. And when it was the day of al-Nahr (the Day of Sacrifice), he would not eat until he had slaughtered."