The Prophet ﷺ said: The mu'adhdhin will receive forgiveness to the extent to which his voice reaches, and every moist and dry place will testify on his behalf; and he who attends (the congregation of) prayer will have twenty-five prayers recorded for him and will have expiation for sins committed between every two times of prayer. (Using translation from Abū Dāʾūd 515)
أَنَّهُ سَمِعَ مِنْ فَمِ رَسُولِ اللهِ ﷺ يَقُولُ الْمُؤَذِّنُ يُغْفَرُ لَهُ مَدَّ صَوْتِهِ وَيَشْهَدُ لَهُ كُلُّ رَطْبٍ وَيَابِسٍ وَشَاهِدُ الصَّلَاةِ يُكْتَبُ لَهُ خَمْسٌ وَعِشْرُونَ حَسَنَةً وَيُكَفَّرُ عَنْهُ مَا بَيْنَهُمَا