God always being loyal and doing what he promises for David is spoken of as if truth and faithfulness were objects that would be with David. The abstract nouns "truth" and "faithfulness" can be translated as adjectives. Alternate translation: "I will always be truthful with him and I will always act faithfully towards him" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-abstractnouns]])