Heat 1 teaspoon of olive oil over medium heat in a large stock pot or saucepan.
Add the diced carrots, diced onion and diced celery to the pot and cook for about 3 to 5 minutes, until the vegetables have begun to soften.
Add the minced garlic to the pot and cook for 1 minute more, until the garlic becomes fragrant.
Add the diced tomato, stock, water, beans (be sure to drain and rinse them!), spinach leaves, thyme and black pepper to the pot.
Cover the pot with a lid and turn the heat up to medium-high until the soup comes to a boil.
Turn the heat down to medium-low and simmer for about 15 minutes, until the beans and tomatoes are soft, and the spinach leaves have wilted completely.
Stir in ¼ teaspoon of salt.