The Book of the Believer · Hadith 30 (#Ḥadīth #30)
Chapter 1 | The Severity of a Believer’s Afflictions
30 - عن محمد بن مسلم قال: سمعت أبا عبد الله (ع) يقول المؤمنُ لا يمضي عليه أربعون ليلةً إلاّ عُرض له أمرٌ يحزِنه، ويُذكّره به.
30. It has been narrated that Muhammad ibn Muslim said: I heard Abu 'Abd Allah saying: No forty nights pass for a believer except a matter befalls him that grieves him and reminds him (of Allah).
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).