Musannaf Ibn Abi Shayba 3:1556

Abu Bakr narrated to us, he said: Zayd ibn al-Hubab narrated to us, he said: Mu'awiyah ibn Salih narrated to us, he said: Yunus ibn Sayf al-'Ansi narrated to me, from al-Harith ibn Ghutayf or Ghutayf ibn al-Harith al-Kindi—Mu'awiyah was in doubt—he said: Whatever I have seen, I have forgotten, [but] I have not forgotten that I saw the Messenger of Allah, may Allah bless him and grant him peace, place his right hand upon his left, meaning in prayer.