Sunan an-Nasa'i, Book 7, Hadith 683 (In-Book) ⓘ

It was narrated that Mujammi' bin Yahya Al-Ansari said: "I was sitting with Abu Umamah bin Sahl bin Hunaif when the Mu'adhdhin called the Adhan. He said: 'Allahu akbar; Allahu Akbar (Allah is the Greatest, Allah is the Greatest),' and he (also) pronounced the takbir twice. Then he said: 'Ashhadu an la ialaha ill-Allah (I bear witness that there is none worthy of worship except Allah),' and he also sent the testimony twice. Then he said: 'Ashhadu anna Muhammadan Rasul-Allah (I bear witness that Muhammad is the Messenger of Allah),' and he (also) sent the testimony twice. Then he said: 'This is what Mu'awiyah bin Abi Sufyan told me, narrating from statement of the Messenger of Allah.'"

أَخْبَرَنَا سُوَيْدُ بْنُ نَصْرٍ، أَنْبَأَنَا عَبْدُ اللَّهِ بْنُ الْمُبَارَكِ، عَنْ مُجَمِّعِ بْنِ يَحْيَى الأَنْصَارِيِّ، قَالَ كُنْتُ جَالِسًا عِنْدَ أَبِي أُمَامَةَ بْنِ سَهْلِ بْنِ حُنَيْفٍ فَأَذَّنَ الْمُؤَذِّنُ فَقَالَ اللَّهُ أَكْبَرُ اللَّهُ أَكْبَرُ فَكَبَّرَ اثْنَتَيْنِ فَقَالَ أَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ فَتَشَهَّدَ اثْنَتَيْنِ فَقَالَ أَشْهَدُ أَنَّ مُحَمَّدًا رَسُولُ اللَّهِ فَتَشَهَّدَ اثْنَتَيْنِ ثُمَّ قَالَ حَدَّثَنِي هَكَذَا مُعَاوِيَةُ بْنُ أَبِي سُفْيَانَ عَنْ قَوْلِ رَسُولِ اللَّهِ صلى الله عليه وسلم ‏.‏