Musnad Ahmad 32:755

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