Musnad Ahmad 32:2128

'Affan narrated to us, Hammad narrated to us, he said: Thabit informed us, from Anas, that the Messenger of Allah (may Allah bless him and grant him peace) said on the day of Uhud, while he was wiping the blood from his face: "How can a people prosper who have wounded the face of their Prophet and broken his incisor tooth, while he was calling them to Allah?" Then Allah, the Almighty and Majestic, revealed: {Not for you is the decision whether He turns to them in mercy or punishes them, for they are indeed wrongdoers} [Al 'Imran: 128].