The abstract noun "faithfulness" can be translated with an adjective. Alternate translation: "Comfort me by showing me that you are faithful to your covenant" (See: [[rc://en/ta/man/jit/figs-abstractnouns]])
The word "word" here is a metonym for the promise that Yahweh made using words. Alternate translation: "as you promised" (See: [[rc://en/ta/man/jit/figs-metonymy]])