The idiom to "count on" means to "wait for" or to "expect." The abstract noun "faithfulness" can be translated as an adverb. Alternate translation: "those who expect him to act faithfully because of his covenant" or "those who wait for him to act because he is faithful to his covenant" (See: [[rc://en/ta/man/translate/figs-idiom]] and [[rc://en/ta/man/translate/figs-abstractnouns]])