مَا أَجْمَلَ الْوَفَاءَ بِالْوَعْدِ!
How admirable it is to keep a promise!
The utterance directly praises promise-keeping. Spoken before someone who broke a promise, it may additionally function as an indirect reproach. The indirect point comes from the situation, not from the literal wording alone.
Kināyah often works through an associated meaning of an expression. This indirect rebuke depends strongly on speaker, audience and occasion. The two mechanisms should not be collapsed.