Melt the margarine in a large pot, then cook the spices, celery, and chopped onions over medium heat for 5 minutes - do not brown.
Add the cilantro and tomatoes with juice and cook for another 15 minutes. Add the water, lentils, chickpeas and salt. Bring to a boil and simmer, partially covered, for about 2 hours (or until the chickpeas are cooked).
Just before serving, stir in the lemon juice and garnish with reserved cilantro sprigs and lemon slices.