Sahih Muslim 6705

Abu Huraira reported Allah's Apostle (ﷺ) as saying Allah has mobile (squads) of angels, who have no other work (to attend to but) to follow the assemblies of Dhikr and when they find such assemblies in which there is Dhikr (of Allah) they sit in them and some of them surround the others with their wings till the space between them and the sky of the world is fully covered, and when they disperse (after the assembly of Dhikr is adjourned) they go upward to the heaven and Allah, the Exalted and Glorious, asks them although He is best informed about them: This hadith had been transmitted on the authority of Anas through another chain of narrators.