اللَّهُ لَا إِلَهَ إِلَّا هُوَ الْحَيُّ الْقَيُّومُ لَا تَأْخُذُهُ سِنَةٌ وَلَا نَوْمٌ لَهُ مَا فِي السَّمَاوَاتِ وَمَا فِي الْأَرْضِ مَنْ ذَا الَّذِي يَشْفَعُ عِنْدَهُ إِلَّا بِإِذْنِهِ يَعْلَمُ مَا بَيْنَ أَيْدِيهِمْ وَمَا خَلْفَهُمْ وَلَا يُحِيطُونَ بِشَيْءٍ مِنْ عِلْمِهِ إِلَّا بِمَا شَاءَ وَسِعَ كُرْسِيُّهُ السَّمَاوَاتِ وَالْأَرْضَ وَلَا يَئُودُهُ حِفْظُهُمَا وَهُوَ الْعَلِيُّ الْعَظِيمُ
Transliteration
Allahu la ilaha illa huwal-hayyul-qayyumu la ta'khudhuhu sinatun wa la nawmun lahu ma fis-samawati wa ma fil-ardi man dhalladhi yashfa'u 'indahu illa bi'idhnihi ya'lamu ma bayna aydihim wa ma khalfahum wa la yuhituna bishay'in min 'ilmihi illa bima sha'a wasi'a kursiyyuhus-samawati wal-arda wa la ya'uduhu hifzuhuma wa huwal-'aliyyul-'azim
English meaning
Allah, there is no deity except Him, the Ever-Living, the Sustainer of existence. Neither drowsiness overtakes Him nor sleep. To Him belongs whatever is in the heavens and whatever is on the earth. Who is it that can intercede with Him except by His permission? He knows what is before them and what will be after them, and they encompass not a thing of His knowledge except for what He wills. His Kursi extends over the heavens and the earth, and their preservation tires Him not. And He is the Most High, the Most Great.
When is it recited?
Recited before going to sleep.
Its virtue
Whoever recites this before sleeping will have a guardian from Allah protecting them until morning, and no devil will come near them.
Source
Al-Baqarah 2:255; Bukhari, Wakalah 10, 2311