Abu Umamah bin Sahl bin Hunayf said: I heard Sayyiduna Mu'awiyah bin Abi Sufyan (may Allah be pleased with him) while he was sitting on the pulpit; the mu'adhdhin gave the adhan and said: 'Allahu akbar, Allahu akbar' (Allah is the Greatest, Allah is the Greatest). Sayyiduna Mu'awiyah (may Allah be pleased with him) said: "Allahu akbar, Allahu akbar." He said: 'Ashhadu an la ilaha illallah' (I bear witness that there is no god but Allah), and Sayyiduna Mu'awiyah (may Allah be pleased with him) said the like of it. He said: 'Ashhadu anna Muhammadan rasulullah' (I bear witness that Muhammad is the Messenger of Allah), and Sayyiduna Mu'awiyah (may Allah be pleased with him) also said: "And I too." Then when he completed the adhan, he said: O people, I heard the Messenger of Allah (peace and blessings be upon him) on this very seat, when the mu'adhdhin gave the adhan, say the same as what you have heard from me.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 1927