Surah Al-Mulk - The 67th Surah of the Holy Quran.

Jabir Radiyallahu ‘anhu narrates that Nabi Sallallahu ‘alaihi wasallam did not use to sleep until he recited Alif Lam Mim Sajdah, (Surah 32) and Tabarakalladhl biyadihil mulk (Surah 67). (Tirmidhi)

Abu Hurairah Radiyallahu ‘anhu narrates that Nabi Sallallahu ‘alaihi wasallam said: Indeed, there is a Surah in the Qur’an having thirty verses, which intercedes for its reciter until he is forgiven. And that Surah is: Tabarakalladhl biyadihil mulk (Surah 67). (Tirmidhi)

Ibne-’Abbas Radiyallahu ‘anhuma narrates that someone, amongst the companions of Nabi Sallallahu ‘alaihi wasallam, set up his tent over a grave, without realizing that it was a grave. Suddenly he heard the person of the grave reciting Surah Mulk, upto to end of the Surah. He came to Nabi Sallallahu ‘alaihi wasallam and said: O Rasulallah I set up my tent unknowingly over a grave, and suddenly I heard someone reciting Surah Mulk up to its end. Nabi Sallallahu ‘alaihi wasallam said: It is the defender; it is the protector which safeguards him from the Punishment in the grave. (Tirmidhi)

Ibne-Mas’ud Radiyallahu ‘anhu narrates that: The torment starts from the side of the feet of a dead man in the grave. The feet say: There is no way for you to come through us, for he used to recite Surah Mulk {Surah 67). Then the torment advances towards him from his chest or the stomach. It says: There is no way for you to come through me, for he used to recite Surah Mulk. Then the torment advances from towards his head. The head says: There is no way for you to come through me, as he used to recite Surah Mulk. (‘Abdullah ibne-Mas’ud says) This Surah prevents the torments of the grave. It was also called Surah Mulk in the Taurat (Torah). He who recites it at night, is indeed blessed with a tremendous reward.
(Mustadrak Hakim)

Reference: islamhadith.com