How to Make It
In a large bowl, cover the dried beans with 2 inches of water and let them soak overnight. Drain and rinse the beans, then transfer them to a medium enameled cast-iron casserole. Add 3 quarts of the water and bring to a simmer over moderate heat, skimming as necessary to remove the foam that rises to the surface. Cook the beans over low heat until almost tender, about 1 hour. Add the tomatoes, garlic, celery leaves, oregano and 1/4 cup of the olive oil. Season with salt. Continue cooking until the beans are very tender, about 1 1/2 hours longer.
Meanwhile, in a large skillet, heat the remaining 1/4 cup of olive oil. Add the onion and cook over low heat until softened but not browned, about 8 minutes. Add the squash and the remaining 1 cup of water, cover and simmer over low heat until the squash is just tender, about 10 minutes.
When the beans are done, stir in the squash. Season with salt and crushed red pepper and simmer for 5 minutes. Serve in shallow soup bowls.