What is the ruling on the muezzin saying "نَشْهَدُ أَن لَا إِلَهَ إِلَّا اللَّهُ" (we bear witness that there is no god but Allah) instead of "أَشْهَدُ أَن لَا إِلَهَ إِلَّا اللَّهُ" (I bear witness that there is no god but Allah) from the Sunnah?

The wording of "Ashhadu" (I bear witness) in the Athan (call to prayer) should not be changed to "Nashhadu" (we bear witness), because the Athan was transmitted with specific wordings. However, this change does not invalidate the Athan because it does not alter the meaning. The majority of jurists hold that a grammatical error (lahn) that does not change the meaning is not detrimental, even if it is disliked. As for a grammatical error that changes the meaning, it invalidates the Athan.