Musnad Abu Ya'la al-Mawsili 2:93

Uqbah ibn Mukram narrated to us, Yunus ibn Bukayr narrated to us, from Muhammad ibn Ishaq, from al-Zuhri, from Sa’id ibn ‘Ubayd, the freed slave of Ibn Azhar, who said: I heard Umar ibn al-Khattab say: "Indeed, the Messenger of Allah (may Allah bless him and grant him peace) forbade you from fasting these two days: the day of your breaking the fast from your fasting (Eid al-Fitr), and the day you eat from the meat of your sacrifice (Eid al-Adha)."