Musnad Ahmad 32:1242

Mahbub ibn al-Hasan narrated to us, from Khalid—meaning al-Hadhdha’—from Muhammad, who said: I asked Anas ibn Malik: "Did Umar perform Qunut?" He said: "Yes, and who is better than Umar? The Messenger of Allah (peace and blessings of Allah be upon him) [did so] after the bowing."