To a large Dutch oven add the olive oil and heat over medium heat. Add the onion, celery, carrots, and garlic. Cook the vegetables for 10 to 12 minutes or until they start to get tender.
Once the vegetables are tender add the beans, cooked chicken, chicken broth, and bay leaf. Turn the heat up to medium-high and bring the soup to a boil.
Once it starts to boil reduce the heat slightly and continue to cook for about 20 to 30 minutes or until the vegetables are cooked. Add the chopped spinach 5 to 10 minutes before the soup is done cooking.