1. In a large pot, heat the olive oil. Add the onion and garlic. Saute until onion is tender and garlic is light brown in color. Add carrot, celery, and sweet potatoes. Cook until vegetables soften, about 5-7 minutes.
2. Stir in the lentils, vegetable broth, and water. Add the diced tomatoes, bay leaves, thyme, and rosemary. Season with salt and pepper and stir. Cook on medium-low heat for about 35-40 minutes or until lentils are cooked.
3. Add the fresh spinach and stir. If necessary, season with salt and pepper. Remove bay leaves and serve warm.