[Machine] I heard Muawiyah say that when the muadhin says "Allahu Akbar" (God is the greatest) two times, Muawiyah also says it two times. And when the muadhin says "Ashhadu allā ilāha illā-llāh" (I bear witness that there is no deity but God) two times, Muawiyah also says it two times. Then he turned towards me and said, "This is how I heard the Messenger of Allah ﷺ say at the time of the call to prayer."
سَمِعْتُ مُعَاوِيَةَ إِذَا كَبَّرَ الْمُؤَذِّنُ اثْنَتَيْنِ كَبَّرَ اثْنَتَيْنِ وَإِذَا شَهِدَ اثْنَتَيْنِ شَهِدَ اثْنَتَيْنِ فَالْتَفَتَ إِلَيَّ فَقَالَ هَكَذَا سَمِعْتُ رَسُولَ اللهِ ﷺ يَقُولُ عِنْدَ الْأَذَانِ