Musnad Ahmad 32:1700

Affan narrated to us, Abdullah bin Bakr—meaning al-Muzani—narrated to us, he said: I heard Ata—meaning ibn Abi Maymunah—narrating, and I do not know it except from Anas: "That the Messenger of Allah (peace and blessings of Allah be upon him) never had a case of retaliation (qisas) brought to him, but that he commanded pardon." Ibn Bakr said: "I used to narrate it from Anas, and they said to me: 'From Anas, without doubt?' So I said: 'I do not know it except from Anas.'"