What is meant by "charred dung" (hammamah) in the Prophetic Tradition, and does the prohibition of using it for istinja' (purification after defecation/urination) include modern products that contain charcoal or volcanic ash?

The Prophet, peace and blessings be upon him, forbade purifying oneself with bones, droppings, and charcoal because the Jinn asked the Prophet, peace and blessings be upon him, for provision. He said: "For you is every bone over which the name of Allah has been mentioned, and it will fall into your hands with the most meat it can have, and every dropping is fodder for your animals." Charcoal is also a provision for them. So the Prophet, peace and blessings be upon him, forbade purifying oneself with them because they are the food of our brothers from among the Jinn. Also, charcoal crumbles and pollutes the area. The jurists inferred that forbidding purification with food and crops is even more appropriate.