Kitāb al-Muʾmin
Hadith 2626 - وعنه (ع) قال: إن الربَّ ليتعاهدُ المؤمنَ؛ فما يمُرّ به أربعون صباحاً إلاّ تعاهده إمّا بمرضٍ في جسده وإما بمصيبة في أهله وماله أو بمصيبة من مصائب الدّنيا ليؤجِرَه الله عليه.
26. It has been also narrated that Abu 'Abd Allah (a.s) said: Verily the Lord maintains a believer; no forty days pass but that He presents him either with an ailment in his body, or with an affliction in his family and wealth, or any other affliction of the world, that He may thereby reward him for that.