عَنْ مُعَاوِيَةَ قَالَ: سَمِعْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ: «الْمُؤَذِّنُونَ أَطْوَلُ النَّاسِ أعناقا يَوْم الْقِيَامَة» . رَوَاهُ مُسلم

Sa‘d b. Abu Waqqas reported God’s Messenger as saying

If anyone says when he hears the mu’adhdhin, “I testify that there is no god but God alone who has no partner and that Muhammad is His servant and Messenger; I am satisfied with God as Lord, with Muhammad as Messenger, and with Islam as religion,” his sins will be forgiven him. Muslim transmitted it.