Musnad Abu Ya'la al-Mawsili 133:6

Abu Khaythama narrated to us, Sufyan ibn 'Uyayna narrated to us, from 'Ali ibn Zayd, from Anas, who said: The Messenger of Allah (may Allah bless him and grant him peace) used to say: "The voice of Abu Talha in the army is better than a battalion." And when he met [the enemy] with the Prophet (may Allah bless him and grant him peace), he would kneel before him and say: "My soul is a ransom for your soul, and my face is a shield for your face."