I am looking for the Hadith which mentions on the Day of Qiyamah, Allah Ta’ala will remind a person of his sins and this person will be unable to deny it. Eventually Allah Ta’ala will convert his sins into good deeds and this person will say that he doesn’t see other evil deeds he carried out. Upon this, Nabi (sallallahu ‘alayhi wa sallam) smiled and his teeth became visible.
You are referring to the following Hadith recorded in Sahih Muslim:
Sayyiduna Abu Dharr (radiyallahu ‘anhu) reports that Rasulullah (sallallahu ‘alayhi wa sallam) said, “I know the last person who will enter Jannah and the last person to come out of Jahannam. He will be a man who will be brought on the Day of Qiyamah and it will be said, ‘Show him his minor sins and withhold the major sins.’
His minor sins would be presented before him, and it would be said, ‘On such and such a day you did so and so and on such and such a day you did so and so.’ He would say, ‘Yes.’ It would not be possible for him to deny them as he would be afraid that his major sins be presented before him [next].
It would be said to him, ‘In place of every evil deed you will have a good deed.’ He will then say, ‘My Rabb! I have done things I do not see here!’”
Upon this, Nabi (sallallahu ‘alayhi wa sallam) smiled, till his molars became visible.
(Sahih Muslim, Hadith: 190)
And Allah Ta’ala Knows best.
Answered by: Moulana Suhail Motala
Approved by: Moulana Muhammad Abasoomar
This answer was collected from HadithAnswers.com. The answers were either answered or checked by Moulana Haroon Abasoomar (rahimahullah) who was a Shaykhul Hadith in South Africa, or by his son, Moulana Muhammad Abasoomer (hafizahullah), who is a Hadith specialist.