Sayyiduna Abu Hurayra (Radhiallaahu Anhu) reports that Rasulullah
(Sallallaahu Alayhi Wasallam) said, 'Verily there is a Surah in the Qur'aan
which has 30 Aayats. It had interceded for a person till he was forgiven.
That Surah is 'Tabaaraka llaahiy biyadihil mulk'.' (Sunan Tirmidhi
Imaam Tirmidhi has classified this narration as Hasan (sound) and Imaam ibn
Hibbaan and al-Haakim regarded it as Sahih (authentic). See Saheeh ibn
Hibbaan vol.3 pg.67-69 and Mustadrak al-Haakim vol.2 pg.498
Sayyiduna ibn Mas'ood (Radhiallaahu Anhu) is reported to have said, 'A man
will be approached in his grave from his legs and from his chest and then
from his head. And each time this Surah will defend him by saying, 'You
cannot do anything to him, he used to recite Surah Mulk'.'
Sayyiduna ibn Mas'ood (Radhiallaahu Anhu) further states, 'It is called,
'Al-maani'ah'. For it protects from the punishment of the grave.' (Mustadrak
al-Haakim vol.2 pg.498). imam Haakim has classified this narration as Saheeh
(authentic) and Haafiz Zahabiy has confirmed this.
and Allah Ta'ala Knows Best