Musnad Abu Ya'la al-Mawsili 106:39

Ishaq narrated to us, Ibn Idris narrated to us, he said: I heard Yazid bin Abi Ziyad, from Ibn Abi Layla, from al-Bara’, who said: I saw the Messenger of Allah (may Allah bless him and grant him peace) raise his hands when he commenced the prayer, until I saw his thumbs near his ears. Then, he did not raise them again.