Here the word "Oh" is used to convey a strong desire for people to praise Yahweh. The abstract noun "faithfulness" can be translated with an adjective. Alternate translation: "Let people praise Yahweh because he is faithful to his covenant" or "People should praise Yahweh because he is faithful to his covenant" (See: [[rc://en/ta/man/translate/figs-exclamations]] and [[rc://en/ta/man/translate/figs-abstractnouns]])