Sahih al-Bukhari, Hadith 914 ⓘ
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 on this very pulpit saying what you have just heard me saying".
حَدَّثَنَا ابْنُ مُقَاتِلٍ، قَالَ أَخْبَرَنَا عَبْدُ اللَّهِ، قَالَ أَخْبَرَنَا أَبُو بَكْرِ بْنُ عُثْمَانَ بْنِ سَهْلِ بْنِ حُنَيْفٍ، عَنْ أَبِي أُمَامَةَ بْنِ سَهْلِ بْنِ حُنَيْفٍ، قَالَ سَمِعْتُ مُعَاوِيَةَ بْنَ أَبِي سُفْيَانَ،، وَهُوَ جَالِسٌ عَلَى الْمِنْبَرِ، أَذَّنَ الْمُؤَذِّنُ قَالَ اللَّهُ أَكْبَرُ اللَّهُ أَكْبَرُ. قَالَ مُعَاوِيَةُ اللَّهُ أَكْبَرُ اللَّهُ أَكْبَرُ. قَالَ أَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ. فَقَالَ مُعَاوِيَةُ وَأَنَا. فَقَالَ أَشْهَدُ أَنَّ مُحَمَّدًا رَسُولُ اللَّهِ. فَقَالَ مُعَاوِيَةُ وَأَنَا. فَلَمَّا أَنْ قَضَى التَّأْذِينَ قَالَ يَا أَيُّهَا النَّاسُ إِنِّي سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم عَلَى هَذَا الْمَجْلِسِ حِينَ أَذَّنَ الْمُؤَذِّنُ يَقُولُ مَا سَمِعْتُمْ مِنِّي مِنْ مَقَالَتِي.
also referenced under: Book 11, Hadith 38 (In-Book) & Volume 2, Book 13, Hadith 37 (USC-MSA)