In verse 50 placing al-maʿrūf before one’s ʿirḍ means making good conduct a protection for honor. Verse 51 sharpens that idea: people may cease relying on a wealthy individual who withholds every benefit.
The lines are more than a technique for gaining fame. They treat trust as the outcome of character and useful action. The following maxim on keeping promises adds another necessary condition of social credibility.