Musnad Ahmad 32:1756

Ali ibn Ishaq narrated to us, he said: Abdullah informed us, he said: Hammad ibn Zayd informed us, from Abd al-Aziz ibn Suhayb, from Anas ibn Malik: "A man stood up to the Messenger of Allah (peace and blessings of Allah be upon him) while he was delivering the sermon, and he mentioned him. He raised his hands—and Abd al-Aziz gestured—and he placed their backs toward his face."