Add thyme, paprika, cumin, and pepper. Cook 1 minute until fragrant.
Boil, then reduce heat to low. Cover and simmer for about 1 1/2 hours or until beans are tender, stirring occasionally. Add more liquid if needed.
Take out the bay leaf. Mix in the chopped spinach and cook for another 5 minutes until it wilts. Adjust seasoning with salt to your preference.