حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا شَبَابَةُ، حَدَّثَنَا شُعْبَةُ، عَنْ مُوسَى بْنِ أَبِي عُثْمَانَ، عَنْ أَبِي يَحْيَى، عَنْ أَبِي هُرَيْرَةَ، قَالَ سَمِعْتُ مِنْ، فِي رَسُولِ اللَّهِ ـ صلى الله عليه وسلم ـ يَقُولُ ‏"‏ الْمُؤَذِّنُ يُغْفَرُ لَهُ مَدَّ صَوْتِهِ وَيَسْتَغْفِرُ لَهُ كُلُّ رَطْبٍ وَيَابِسٍ وَشَاهِدُ الصَّلاَةِ يُكْتَبُ لَهُ خَمْسٌ وَعِشْرُونَ حَسَنَةً وَيُكَفَّرُ عَنْهُ مَا بَيْنَهُمَا ‏"‏ ‏.‏

It was narrated that Abu Hurairah said: "I heard the Messenger of Allah himself say: 'The Mu'adh-dhin's sins will be forgiven as far as his voice reaches, and every wet and dry thing will pray for forgiveness for him. For the one who attends the prayer, twenty-five Hasanat (good deeds) will be recorded, and it is will be expiation (for sins committed) between them (the two prayers).'" Translation Not Available

Book Ref: Sunan Ibn Majah Book 3 Hadith 724
Web Ref:  Sunan Ibn Majah Vol 1 Book 3 Hadith 724