Musnad Ahmad 32:1195

Ibn Abi ‘Adi narrated to us, from Humayd, from Anas, who said: On the day of Uhud, the incisor tooth of the Messenger of Allah, may Allah bless him and grant him peace, was broken, and his face was wounded. He said: The blood began to flow down his face, and he began to wipe the blood from his face, saying: "How can a people prosper who have stained the face of their Prophet with blood, while he is calling them to Allah?" He said: Then Allah revealed: {Not for you is the decision whether He should forgive them or punish them, for they are indeed wrongdoers} [Al ‘Imran: 128].