Fath al-Rabbani

Benefits: … Every good, fleshy bone—by this is meant that Allah, the Exalted, again produces flesh upon that bone, which the jinn eat. As for dung and droppings, these have been declared, in an absolute sense, as the food for the cattle of the jinn.

In Sahih Bukhari, there is a narration from Sayyiduna Abu Hurairah radi Allahu anhu, in which he says: When the Prophet sallallahu alayhi wa sallam finished relieving himself, I asked: What is the reason for not performing istinja (purification after relieving oneself) with bones and dung? The Prophet sallallahu alayhi wa sallam replied: ((They are from the food of the jinn. Indeed, a delegation of the jinn of Nasibin came to me—and they are excellent jinn—and they asked me for provision. So I supplicated to Allah for them that whenever they pass by a bone or dung, they find food upon it.)) … These two things are from the food of the jinn. A delegation of the jinn of Nasibin came to me; they were the best of the jinn, and they asked me about provision. So I supplicated to Allah, the Exalted, that whenever they pass by a bone or dung, they find food upon it.

From these narrations, it is understood that bones, dung, and droppings—these things are not the food of the jinn and their cattle themselves, but rather, their food is placed upon them. Allah, the Exalted, knows best what the form of that food is and how they benefit from these things. A scholar used to say that since the jinn are a subtle (latif) creation, they obtain nourishment from these things by smelling them. And Allah knows best.