Musnad Ahmad 994:1

'Abd al-Rahman ibn Mahdi narrated to us, Mu'awiyah narrated to us, from Yunus ibn Sayf, from al-Harith ibn Ghutayf—or Ghutayf ibn al-Harith—who said: Of the things I have forgotten, I have not forgotten that I saw the Messenger of Allah, peace and blessings of Allah be upon him, placing his right hand upon his left in prayer.