Musnad Ahmad 2:201

I read to Abd al-Rahman: From Malik, from Ibn Shihab, from Abu Ubayd, the freed slave of Ibn Azhar, that he said: I witnessed the Eid with Umar ibn al-Khattab. He came and prayed, then departed and addressed the people. He said: "Indeed, these are two days on which the Messenger of Allah, may Allah bless him and grant him peace, forbade fasting: the day of your breaking your fast, and the other is the day you eat from your sacrifice."