Musnad Ahmad 2:143

'Abd al-Razzaq narrated to us, Ma'mar informed us, from al-Zuhri, from Abu 'Ubayd, the freed slave of 'Abd al-Rahman ibn 'Awf: That he witnessed the 'Eid with 'Umar ibn al-Khattab. He prayed before he delivered the sermon, without an adhan or an iqamah. Then he delivered the sermon and said: "O people, the Messenger of Allah, may Allah bless him and grant him peace, forbade fasting on these two days. As for one of them, it is the day of your breaking your fast from your fasting and your 'Eid. As for the other, it is the day you eat from your sacrificial animals."