«وَالدُّعَاءُ يَقِي، وَالْمَدْحُ يُنَقِّي»
Prayer protects; praise purifies a person's reputation.
Duʿāʾ is supplication; madḥ is praise. The sounds of yaqī / yunaqqī create a pleasing paired cadence, while the meaning moves from sought protection to the cleansing effect of good mention.
This is a petitioner’s rhetorical claim within an ornate letter, not a literal guarantee that every compliment or prayer must produce an immediate worldly result. The phrase helps connect generosity with gratitude.