Sahih Muslim 266
صحيح مسلم#266SahihIt is narrated on the authority of 'Abdullah b. Mas'ud that the Messenger of Allah (ﷺ) observed:None shall enter the Fire (of Hell) who has in his heart the weight of a mustard seed of Iman and none shall enter Paradise who has in his heart the weight of a mustard seed of pride
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: 1:172