Musnad Abu Ya'la al-Mawsili 42:161

'Abd al-A'la narrated to us, Hammad narrated to us, from Abu Harun al-'Abdi, from Abu Sa'id and Bishr ibn Harb, from Abu Sa'id: That the Messenger of Allah (may Allah bless him and grant him peace) forbade fasting on the day of al-Fitr and the day of al-Nahr (sacrifice). And he forbade prayer after the dawn prayer until the sun rises, and after the 'Asr (afternoon) prayer until the sun sets. And Abu Harun said: Abu Sa'id said: "Fast whenever you wish, and pray whenever you wish."