Musnad Ahmad 32:1196

Ibn Abi ‘Adi narrated to us, from Humayd, from Anas, who said: "Abu Talhah was in front of the Messenger of Allah, may Allah bless him and grant him peace, and the Messenger of Allah, may Allah bless him and grant him peace, would raise his head from behind him to look at the places where his arrows landed. Abu Talhah would stretch his chest out to shield the Messenger of Allah, may Allah bless him and grant him peace, and say: 'O Messenger of Allah, my throat is a shield for your throat.'"