Musnad Abu Ya'la al-Mawsili 114:9

Abu Khaythama narrated to us, Ismail narrated to us, from Ayyub, from Muhammad, who said: I said to Anas, "Did the Messenger of Allah (peace and blessings of Allah be upon him) perform Qunut in the morning prayer?" He said, "Yes, after the bowing (ruku)." He said: Then he was asked after that, "Did the Messenger of Allah (peace and blessings of Allah be upon him) perform Qunut in the morning prayer?" He said, "Yes, after the bowing (ruku), for a short while."