Add the onion, celery, carrots and garlic and sauté until golden, about 10 minutes.
Stir in the chili powder, ginger, bay leaf, and dried crushed red pepper. Add 9 ½ cups water and dried lentils and bring to boil. When the soup is boiling, reduce heat to medium-low and simmer uncovered until lentils are tender, about 35 minutes. Add the spinach, and simmer until spinach is wilted, around 5 minutes.