Sahih Muslim , Book 7, Hadith 36 (In-Book) ⓘ

Abu Huraira reported Allah's Messenger as saying: There is an angel on every door of the mosque recording him first who (comes) first (to the mosque for Friday prayer). And he [the Prophet] likened him to one who offers a camel as a sacrifice and then he went on in the descending order till he reached the point at which the minimum (sacrifice) is that of an egg. And when the Imam sits (on the pulpit) the sheets are folded and they (the angels) attend to the mention of Allah.

وَحَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا يَعْقُوبُ، - يَعْنِي ابْنَ عَبْدِ الرَّحْمَنِ - عَنْ سُهَيْلٍ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ عَلَى كُلِّ بَابٍ مِنْ أَبْوَابِ الْمَسْجِدِ مَلَكٌ يَكْتُبُ الأَوَّلَ فَالأَوَّلَ - مَثَّلَ الْجَزُورَ ثُمَّ نَزَّلَهُمْ حَتَّى صَغَّرَ إِلَى مَثَلِ الْبَيْضَةِ - فَإِذَا جَلَسَ الإِمَامُ طُوِيَتِ الصُّحُفُ وَحَضَرُوا الذِّكْرَ ‏" ‏ ‏.