Muhammad bin Yusuf (may Allah have mercy on him), the freed slave of the family of Uthman, said: The mu'adhdhin called the adhan and said: Allahu akbar, and Mu'awiyah (may Allah be pleased with him) said: "Allahu akbar." The mu'adhdhin said: I bear witness that there is no god but Allah, and Mu'awiyah (may Allah be pleased with him) said: "I bear witness that there is no god but Allah." The mu'adhdhin said: I bear witness that Muhammad (peace and blessings be upon him) is the Messenger of Allah, and Mu'awiyah (may Allah be pleased with him) said: "I bear witness that Muhammad (peace and blessings be upon him) is the Messenger of Allah." Then Mu'awiyah (may Allah be pleased with him) said: "This is how I heard the Messenger of Allah (peace and blessings be upon him)."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 16853