Sahih Muslim 7219
صحيح مسلم#7219SahihAl-Bara' b. `Azib reported Allah's Apostle (ﷺ) as saying:This verse: "Allah grants steadfastness to those who believe with firm word," was revealed in connection with the torment of the grave. It would be said to him: Who is your Lord? And he would say: Allah is my Lord and Muhammad is my Apostle (ﷺ), and that is (what is implied) by the words of Allah, the Exalted: "Allah keeps steadfast those who believe with firm word in this world and in the Hereafter
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 53:88