Musnad Abu Ya'la al-Mawsili 219:21

Bandar narrated to us, he said: Abd al-Rahman and Bahz narrated to me, from Shu'bah, from Abu Bishr, from Abu al-Malih, from Abdullah ibn Utbah, from Umm Habibah, from the Prophet (peace and blessings of Allah be upon him) that he said: "Say as the mu'adhdhin says, until he falls silent."