Sunan Ibn Majah, Volume 1, Book 3, Hadith 712 (DarusSalam) ⓘ
It was narrated that Ibn 'Umar said: "The Messenger of Allah said: There are two characteristics in which the Muslims are dependent upon their Mu'adh-dhins: their prayer and their fasting."
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُصَفَّى الْحِمْصِيُّ، حَدَّثَنَا بَقِيَّةُ، عَنْ مَرْوَانَ بْنِ سَالِمٍ، عَنْ عَبْدِ الْعَزِيزِ بْنِ أَبِي رَوَّادٍ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ " خَصْلَتَانِ مُعَلَّقَتَانِ فِي أَعْنَاقِ الْمُؤَذِّنِينَ لِلْمُسْلِمِينَ صَلاَتُهُمْ وَصِيَامُهُمْ " .
also referenced under: Hadith 712 (Reference) & Book 3, Hadith 7 (In-Book)