The writer speaks of Yahweh acting favorably towards him as if Yahweh's face shone a light on him. Alternate translation: "Act favorably towards your servant" (See: [[rc://en/ta/man/translate/figs-metaphor]])
The abstract noun "faithfulness" can be translated as an adjective. Alternate translation: "save me because you are faithful to your covenant" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])