The Messenger of Allah said: "Whoever says, when he hears the Mu'adh-dhin, 'Wa ana Ash-hadu an la ilaha illallah wahdahu la sharika lahu, wa ash-hadu anna Muhammadan 'abduhu wa rasuluhu, radaytu Billahi rabban wa bil-islami dinan wa bi muhammadin nabiyyan (And I bear witness that none has the right to be worshipped but Allah alone, with no partner, and I bear witness that Muhammad is His slave and Messenger, and I am content with Allah as my Lord, Islam as my religion and Muhammad as my Prophet),' his sins will be forgiven to him."

عَنْ رَسُولِ اللَّهِ ﷺ أَنَّهُ قَالَ مَنْ قَالَ حِينَ يَسْمَعُ الْمُؤَذِّنَ وَأَنَا أَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ وَحْدَهُ لاَ شَرِيكَ لَهُ وَأَشْهَدُ أَنَّ مُحَمَّدًا عَبْدُهُ وَرَسُولُهُ رَضِيتُ بِاللَّهِ رَبًّا وَبِالإِسْلاَمِ دِينًا وَبِمُحَمَّدٍ نَبِيًّا غُفِرَ لَهُ ذَنْبُهُ

If anyone says when he hears the MU’ADHDHIN : “And I testify that there is no god but Allah alone who has no partner and that Muhammad is His servant and Apostle: I am satisfied with Allah as lord, with Muhammad as apostle and with Islam as religion”, he will be forgiven. (Using translation from Abū Dāʾūd 525)

عَنْ رَسُولِ اللَّهِ ﷺ قَالَ «مَنْ قَالَ حِينَ يَسْمَعُ الْمُؤَذِّنَ وَأَنَا أَشْهَدُ أَنْ لَا إِلَهَ إِلَّا اللَّهُ وَحْدَهُ لَا شَرِيكَ لَهُ وَأَشْهَدُ أَنَّ مُحَمَّدًا عَبْدُهُ وَرَسُولُهُ رَضِيتُ بِاللَّهِ رَبًّا وَبِالْإِسْلَامِ دِينًا وَبِمُحَمَّدٍ ﷺ رَسُولًا غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ»

"مَنْ قَال حِينَ يَسْمَعُ الْمُؤَذِّنَ: وَأَنَا أَشْهَدُ أَنْ لا إِلهَ إِلا الله وَحْدَهُ لا شَرِيكَ لَهُ، وَأَشْهَدُ أَنَّ مُحَمَّدًا عَبْدُهُ وَرَسُولُهُ، رَضِيتُ بِالله رَبّا، وَبِمُحَمَّدٍ رَسُولًا، وَبِالإسْلَامِ دِينًا غَفَر الله لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ".