Sahih Muslim
The Book Pertaining to Paradise, Its Description, Its Bounties and Its Intimates (Kitab Al-Jannat wa Sifat Naimiha wa Ahliha)
Book Number: 040 / Hadith Number: 6866
Al-Bara' b. 'Azib reported that this verse:" Allah keeps steadfast those who believe with firm word in th;s world and the Hereafter," was revealed in con- nection with the torment of the grave.