Sahih Bukhari

Narrated Abu Umama bin Sahl bin Hunaif:I heard Muawiya bin Abi Sufyan (repeating the statements of the Adhan) while he was sitting on the pulpit. When the Mu'adh-dhin pronounced the Adhan saying, ""Allahu-Akbar, Allahu Akbar"", Muawiya said: ""Allah Akbar, Allahu Akbar."" And when the Mu'adh-dhin said, ""Ash-hadu an la ilaha illal-lah (I testify that none has the right to be worshipped but Allah)"", Muawiya said, ""And (so do) I"". When he said, ""Ash-hadu anna Muhammadan Rasulullah"" (I testify that Muhammad is Allah's Apostle), Muawiya said, ""And (so do) I"". When the Adhan was finished, Muawiya said, ""O people, when the Mu'adh-dhin pronounced the Adhan I heard Allah's Messenger (ﷺ) on this very pulpit saying what you have just heard me saying