Musnad Abu Ya'la al-Mawsili 117:127

Shayban narrated to us, Amarah narrated to us, Thabit narrated from Anas that the Mu'adhdhin—or Bilal—would perform the Iqamah, and the Messenger of Allah (ﷺ) would enter. A man would meet him and stand with him, until most of them would nod their heads [in drowsiness].