Brown the Italian sausage in a large pot over medium heat until fully cooked.
Drain the excess fat.
Add the onions, carrots, and celery to the pot with the sausage.
Cook for about 5 minutes until the vegetables are softened.
Stir in the garlic and sauté for an additional minute.
Be sure the garlic becomes fragrant but does not burn.
Add the lentils, chicken broth, diced tomatoes, salt, black pepper, oregano, and thyme.
Bring everything to a gentle boil.
Reduce the heat, cover the pot, and let it simmer for about 1 hour until the lentils are tender.