Riyad-us-Saliheen 1448
Abu Hurairah and Abu Sa'id Al-Khudri (May Allah be pleased with them) reported: The Messenger of Allah (PBUH) said, "When a group of people assemble for the remembrance of Allah, the angels surround them (with their wings), (Allah's) mercy envelops them, Sakinah, or tranquillity descends upon them and Allah makes a mention of them before those who are near Him."
[Muslim]
This Hadith also highlights the merits of remembrance of Allah and the high grades of the people indulging in it.