"I was with Mu'awiyah when the Mu'adhdhin called the Adhan. Muawiyah said what the Mu'adhdhin said, but when he said: 'Hayya 'alas-salah (come to prayer),' he said: 'La hawla wa la quwwata illa Billah (There is no power and no strength except with Allah);' and when he said: 'Hayya 'alal-falah (come to prosperity),' he said: 'La hawla wa la quwwata illa Billah (There is no power and no strength except with Allah).' After that he said what the Mu'adhdhin said, then he said: 'I heard the Messenger of Allah ﷺ saying exactly like that.'"  

إِنِّي عِنْدَ مُعَاوِيَةَ إِذْ أَذَّنَ مُؤَذِّنُهُ فَقَالَ مُعَاوِيَةُ كَمَا قَالَ الْمُؤَذِّنُ حَتَّى إِذَا قَالَ حَىَّ عَلَى الصَّلاَةِ قَالَ لاَ حَوْلَ وَلاَ قُوَّةَ إِلاَّ بِاللَّهِ فَلَمَّا قَالَ حَىَّ عَلَى الْفَلاَحِ قَالَ لاَ حَوْلَ وَلاَ قُوَّةَ إِلاَّ بِاللَّهِ وَقَالَ بَعْدَ ذَلِكَ مَا قَالَ الْمُؤَذِّنُ ثُمَّ قَالَ سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ مِثْلَ ذَلِكَ