Gather the ingredients.
Stir chicken broth, water, carrots, celery, onion, lentils, garlic, and red wine vinegar together in a large stockpot; bring to a boil, reduce heat to low, and simmer until carrots are tender, about 10 minutes.
Stir in ham, mustard, salt, and pepper; simmer until lentils are tender, 20 to 30 minutes more.
