Sunan an-Nasa'i 679
سنن النسائي#679Sahihأَخْبَرَنَا قُتَيْبَةُ، عَنِ اللَّيْثِ، عَنِ الْحُكَيْمِ بْنِ عَبْدِ اللَّهِ، عَنْ عَامِرِ بْنِ سَعْدٍ، عَنْ سَعْدِ بْنِ أَبِي وَقَّاصٍ، عَنْ رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ " مَنْ قَالَ حِينَ يَسْمَعُ الْمُؤَذِّنَ وَأَنَا أَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ وَحْدَهُ لاَ شَرِيكَ لَهُ وَأَنَّ مُحَمَّدًا عَبْدُهُ وَرَسُولُهُ رَضِيتُ بِاللَّهِ رَبًّا وَبِمُحَمَّدٍ رَسُولاً وَبِالإِسْلاَمِ دِينًا غُفِرَ لَهُ ذَنْبُهُ " .
It was narrated from Sa'd bin Abi Waqqas that the Messenger of Allah (S.A.W) said:"Whoever says, when he hears the Mu'adhdhin: 'Ashhadu an la ilaha illallah wahdahu la sharika lahu wa anna Muhammadan 'abduhu wa Rasuluhu, raditu Billahi Rabban, wa bil-Islami dinan was bi Muhammadin Rasula (I bear witness that there is none worthy of worship except Allah alone, with no partner or associate, and that Muhammad is the His slave and Messenger; I am content with Allah as my Lord, Islam as my religion and Muhammad as my Messenger),' his sins will be forgiven
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
In-book reference: 7:54