Musnad Ahmad 2:82

Sufyan narrated to us, from al-Zuhri, who heard Abu 'Ubayd say: I witnessed the 'Eid with 'Umar. He began with the prayer before the sermon, and he said: "Indeed, the Messenger of Allah (may Allah bless him and grant him peace) forbade fasting on these two days. As for the day of Fitr, it is the breaking of your fast. And as for the day of Adha, eat from the meat of your sacrifice."