The Prophet would not sleep until he recited Surah as Sajdah.
[Tirmidhi 5/165; Hakim 2/412 & Dhahabi in Sahih al Jamiea (22/789)]

Khalid ibn Ma'dan (radiAllahu anhu) said, 'Recite the Deliverer, which is Alif Laam Tanzeel, for I have heard that a man who had committed many sins used to recite it and nothing else. It spread its wing over him and said, 'O' My Lord, forgive him, for he often used to recite me.' So the Lord Most High made it an intercessor for him and said, 'Record for him a good deed and raise him a degree in place of every sin.'

Khalid (radiAllahu anhu) also said, 'It will dispute on behalf of the one who recites it when he is in his grave saying, 'O' Allah, if I am part of Thy Book, make me an intercessor for him. But if I am not a part of Thy Book, blot me out of it.' It will be like a bird putting its wing on him, it will intercede for him and will protect him from the punishment in the grave. He said the same about Tabaarakalladhi (Surah Mulk).