Musnad Ahmad 1233:2

Husayn ibn Muhammad narrated to us, Khalaf narrated to us, from Abu Malik, who said: My father had prayed behind the Messenger of Allah (peace and blessings of Allah be upon him) when he was sixteen years old, and [he also prayed behind] Abu Bakr, Umar, and Uthman. I said to him: "Did they perform Qunut?" He said: "No, my son, it is a newly invented matter."