Musnad Ahmad 658:220

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Yazid ibn Abi Ziyad, who said: I heard Ibn Abi Layla say: I heard al-Bara' narrating to a group of people, among whom was Ka'b ibn 'Ujrah, saying: "I saw the Messenger of Allah, may Allah bless him and grant him peace, when he commenced the prayer, he raised his hands."