The night before soak beans in water in a covered bowl. Rinse and drain when ready to make soup.
In a large heavy pot combine beans with ham bone, bay leaf, and 12 cups water. Bring to a boil and reduce heat and simmer for 1 hour or until beans are tender. Stir in onion, celery, carrot, potato and garlic. Add packet of seasoning that comes with beans or season to your own taste. Simmer for another hour or so until soup is thick.
Remove ham bone and trip remaining meat from bone, discarding the rind and fat and bone. Stir meat into soup and season with salt and pepper to taste. Stir in parsley and serve.