Musannaf Ibn Abi Shayba 21:594

Hushaym narrated to us, he said: Ibn Abi Layla informed us, from ‘Ata’, from ‘Ubayd ibn ‘Umayr, who said: I prayed behind ‘Umar ibn al-Khattab at dawn, and he said in his Qunut: "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 towards You we strive and hasten, and we hope for Your mercy and fear Your punishment; indeed, Your punishment will overtake the disbelievers."