In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté for about 3-4 minutes until translucent.
Stir in the minced garlic, diced carrots, and celery, and continue to sauté for another 5 minutes until they begin to soften.
Add the chickpeas, vegetable broth, thyme, and basil to the pot. Bring the mixture to a boil, then reduce heat to low and let it simmer for 20 minutes.
After the soup has simmered, stir in the chopped spinach, lemon juice, and lemon zest. Allow it to cook for an additional 5 minutes.
Season the soup with salt and pepper to taste.
Remove from heat and let cool slightly before serving.
Ladle the soup into bowls, garnishing with fresh parsley if desired.