Musannaf Ibn Abi Shayba 3:33

Ibn Idris narrated to us, from ‘Asim ibn Kulayb, from his father, from Wa’il ibn Hujr, who said: I came to al-Madinah and said, "I will certainly look at the prayer of the Prophet, may Allah bless him and grant him peace." He said: So he said the takbir and raised his hands until I saw his thumbs near his ears.