The abstract noun "faithfulness" can be translated with an adjective. AT: "he does great things for us because he is faithful to his covenant" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])
The abstract noun "trustworthiness" can be translated with an adjective or a verbal phrase. AT: "Yahweh remains trustworthy forever" or "Yahweh will forever be worthy of people trusting him" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])