Musnad Ahmad 3:112

'Uthman ibn 'Umar narrated to us, Ibn Abi Dhi'b narrated to us, from Sa'id ibn Khalid ibn 'Abdullah ibn Qariz, from Abu 'Ubayd, the freed slave of 'Abd al-Rahman ibn Azhar, who said: I saw 'Ali and 'Uthman praying on the day of al-Fitr and al-Adha, then they would depart and remind the people. He said: And I heard them both saying: "Indeed, the Messenger of Allah, may Allah bless him and grant him peace, forbade fasting on these two days." He said: And I heard 'Ali saying: "The Messenger of Allah, may Allah bless him and grant him peace, forbade that any of your sacrificial meat remains with you after three [days]."