Musnad Abu Ya'la al-Mawsili 115:72

Muhammad ibn Khalid ibn Abdullah al-Tahhan narrated to us, my father narrated to us, Sa'id narrated to us, from Qatadah, from Anas, that the Messenger of Allah (may Allah bless him and grant him peace) forbade fasting on five days of the year: the day of al-Fitr, the day of al-Nahr (Sacrifice), and the three days of al-Tashriq.