Ayatul Kursi - Surah Al Baqarah 2:255 

Whoever reads Ayatul Kursi when he lies down to sleep will have a guardian from Allah remain with him and Satan will not be able to come near him until he rises in the morning.

اللَّهُ لَآ إِلٰهَ إِلَّا هُوَ الْحَىُّ الْقَيُّومُ لَا تَأْخُذُهُ سِنَةٌ وَلَا نَوْمٌ لَّهُ مَا فِى السَّمٰوٰتِ وَمَا فِى الْأَرْضِ مَنْ ذَا الَّذِى يَشْفَعُ عِندَهُ إِلَّا بِإِذْنِه يَعْلَمُ مَا بَيْنَ أَيْدِيهِمْ وَمَا خَلْفَهُم وَلَا يُحِيطُونَ بِشَىْءٍ مِّنْ عِلْمِهِۦٓ إِلَّا بِمَا شَآءَ وَسِعَ كُرْسِيُّهُ السَّمٰوٰتِ وَالْأَرْض

وَلاَ يَؤُودُهُ حِفْظُهُمَا وَهُوَ الْعَلِىُّ الْعَظِيم

Allah! There is none worthy of worship but He, the Ever Living, the One Who sustains and protects all that exists. Neither slumber nor sleep overtakes Him To Him belongs whatever is in the heavens and whatever is on the earth. Who is he that can intercede with Him except with His Permission? He knows what happens to them in this world, and what will happen to them in the Hereafter.

And they will never compass anything of His Knowledge except that which He wills. His Throne extends over the heavens and the earth, and He feels no fatigue in guarding and preserving them. And He is the Most High, the Most Great.

Allaahu laa 'ilaaha 'illaa Huwal-Hayyul-Qayyoom laa ta'khuthuhu sinatun wa laa nawm, lahu maa fis-samaawaati wa maafil-'ardh, man thal-lathee yashfa'u 'indahu 'illaa bi'ithnih,

ya'lamu maa bayna 'aydeehim wa maa khalfahum, wa laa yuheetoona bishay'im-min 'ilmihi 'illaa bimaa shaa'a, wasi'a kursiyyuhus-samaawaati wal'ardh, wa laa ya'ooduhu hifdhuhumaa, wa Huwal-'Aliyyul- 'Adheem.

 

Soorah al-Baqarah: Ayah(255)

Al-Baqarah 2:255, Al-Bukhari, Fathul Bari 4/487, No 2311

An-Nasa'i, 'Amalul-Yawm wal-Laylah (Hadith no. 100), also Ibn As-Sunni (no. 121). See aso Al-Albani, Sahihul-Jami' As-Saghir 5/339 and Silsilatul-Ahadith As-Sahihah 2/697 (no. 972).