[13].Surah Ar-Ra'd [The Thunder] : Ayat 28-29

Ayat 28. Those who believe (in the Oneness of Allah - Islamic Monotheism), and whose hearts find rest in the remembrance of Allah, Verily, in the remembrance of Allah do hearts find rest .

Ayat 29. Those who believe (in the Oneness of Allah - Islamic Monotheism), and work righteousness, Tu'uba' (it means all kinds of happiness or name of a tree in Paradise) is for them and a beautiful place of (final) return. 

Hazrat Abu Hurairah and Abu Sa`id Al-Khudri (May Allah be pleased with them) reported: The Messenger of Allah  [SAWW](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 tranquility descends upon them and Allah makes a mention of them before those who are near Him.'' [Muslim Book 35, Chapter 11, Hadith # 6518]. 

Lesson : as mentioned above in Surah Ar-Ra'd Ayat 28. "and whose hearts find rest in the remembrance of Allah, Verily, in the remembrance of Allah do hearts find rest." This Hadith also highlights the merits of remembrance of Allah and the high grades of the people indulging in it.