The Book of the Believer · Hadith 97 (#Ḥadīth #5)
Chapter 4 | The Rights of a Believer on a Fellow Believer.
97 - وعن أبي عبد الله (ع) قال ما عُبدَ اللهُ بشئ أفضلَ من أداء حقّ المؤمنِ.
97. It has been reported that Abu 'Abd Allah said: Allah has never been worshipped with anything better than fulfilling the right of a believer.
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).