The Book of the Believer · Hadith 129 (#Ḥadīth #23)
Chapter 5 | The Reward of Helping a Believer, Relieving Him of Distress And Showing Him Kindness
129- وعن أبي عبد الله عليه السلام قال: أوحى الله عز وجل إلى موسى ابن عمران: إن من عبادي من يتقرب إلي بالحسنة، فاحكمه بالجنة. قال: يا رب وما هذه الحسنة؟ قال: يدخل على مؤمن سرورا
129. It has been reported that Abu 'Abd Allah said: Allah revealed to Musa ibn 'Imran: Amongst My servants, I decree Paradise for one who draws near to Me by a certain good deed. 'O Lord,' Musa asked, 'what is this good deed?' 'This is bringing joy to a believer,' He replied.
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).