Ibn Majah 69

Sourcing, Bukhari narrated it in the Book of Faith, chapter on the believer's fear that his deeds might come to nothing without his realizing it, and so on, hadith no. 48, from the hadith of Abu Waail with this wording. Muslim narrated it in the Book of Faith, chapter explaining the Prophet's ﷺ statement, hadith no. 64. Both of them narrated it, Bukhari, no. 7076, and Muslim, from the hadith of Amash with this wording, hadith no. 64.