Musnad Ahmad 200:5

Yazid ibn Harun narrated to us, he said: Abu Malik informed us, he said: I said to my father: "O my father, you have prayed behind the Messenger of Allah (may Allah bless him and grant him peace), and Abu Bakr, and Umar, and Uthman, and Ali here in Kufa, for nearly five years. Did they perform Qunut?" He said: "O my son, it is an innovation."