Heat oil over low heat in a large soup kettle while preparing the vegetables. When ready to sauté, increase heat to medium-high and add onions, carrot, and celery; sauté until soft, about 5 minutes. Add oregano, followed by broth and 2 cups of water and the rice and beans. Bring to a simmer; reduce heat to medium-low and cook to blend flavors, about 5 minutes. Pull off 2 cups of the soup and puree in a blender or food processor; return to the pot. Add lemon juice and zest and spinach and dill; return to a simmer. Taste and adjust seasoning, including a generous sprinkling of salt and pepper. Serve.