Sort and rinse lentils.
In large soup pot, heat oil over medium heat and add onion, carrots, and celery. Cook and stir until onions are tender.
Stir in garlic, oregano, bay leaf, and basil.
Cook for 2 minutes.
Stir in lentils, tomatoes and water. Bring to a boil.
Reduce heat, simmer for at least 1 hour.
When ready to serve, stir in spinach, and cook until spinach wilts.
Stir in vinegar, and season to taste with salt and pepper. Add more vinegar if desired.
General cooking directions for lentils: Add lentils to any of your favourite recipes. Add 1.5 L (6 cups) of hot water to sorted and rinsed lentils. Simmer 30-40 minutes or until tender. Salt and flavour to taste.