Musannaf Ibn Abi Shayba 21:596

Hushaym narrated to us, he said: Husayn informed us, he said: I prayed the morning prayer one day, and Uthman ibn Ziyad prayed behind me. He said: So I performed the Qunut in the morning prayer. He said: When I finished my prayer, he said to me: "What did you say in your Qunut?" I said: "I mentioned these words: O Allah, we seek Your help and we seek Your forgiveness, and we praise You with goodness and we do not disbelieve in You, and we cast off and abandon whoever acts wickedly against You. O Allah, You alone we worship, and to You we pray and prostrate, and to You we strive and hasten, and we hope for Your mercy and fear Your punishment; indeed, Your punishment will overtake the disbelievers." He said: Uthman said to me: "This is how Umar ibn al-Khattab and Uthman ibn Affan used to do."