Cover beans with cold water and soak over night. Change the water and cook at slightly below boiling point until skins burst. To test beans, take a few and expose them to cold air; if shells burst, they are sufficiently cooked. Drain off the water and add the salt pork which has been cut into strips. Put in bean pot, having some of the salt pork slices on top. Mix the mustard, sugar, salt, and molasses together and add to the beans. Add the boiling water. Cover pot and bake at 250-F about 6 hours, removing the cover during the last hour.