Musnad Ahmad 1159:9

Muhammad ibn Ja‘far narrated to us, he said: Shu‘bah narrated to us, from Abu Bishr, from Abu al-Malih, from Umm Habibah, from the Prophet, may God bless him and grant him peace, that: "When he would hear the muezzin calling the adhan, he would say as he says, until he fell silent."