In a large stock pot over med-high heat, heat oil, reduce heat to medium low, add onions and celery until softened, about 5 minutes.
Add all remaining ingredients and simmer over low heat for 1 1/2 to 2 hours, stirring often.
Notes
1 cup dried lentils yields about 2 1/2 cups cooked. Simply add 4 cups water to a saucepan with the lentils, bring to boil and reduce to simmer for 40 minutes. Drain.Or you can use prepared canned lentils!