Soak beans overnight in about 2 quarts water. Drain off water, then add water to cover and cook gently until beans are tender, about 1 hour. Meanwhile, steam squash until tender. Cool slightly and puree. In a heavy soup kettle, heat oil and saute onions, celery, ginger, and garlic until soft. Add squash puree. Add cooked beans, bean liquid, and about 2 cups water. Add salt and pepper to taste. Add additional water, if necessary, for desired consistency. Serve hot, garnished with parsley.