Musannaf Ibn Abi Shayba 3:3868

Mu'tamir ibn Sulayman narrated to us, from 'Amarah al-Saydalani, from Thabit al-Bunani, who said: I used to be with Anas, and he would come upon a mosque and hear the Adhan, so he would say, "Is this a newly invented one?" And if they said, "Yes," he would pass by it to another.