Musnad Ahmad 33:973

Muhammad ibn al-Hasan al-Wasiti—meaning al-Muzani—narrated to us, Abu Yusuf al-Hajjaj—meaning ibn Abi Zaynab al-Sayqal—narrated to us, from Abu Sufyan, from Jabir, who said: "The Messenger of Allah (ﷺ) passed by a man while he was praying, and he had placed his left hand upon his right. So he pulled it away, and placed the right upon the left."