Which of the two opinions on the impurity of unknown-source dung is stronger: that which deems it impure based on the principle that the original state of dung is impurity, or that which deems it pure based on the principle that the original state of substances is purity, and what is the reason for preferring one over the other?

The jurists who hold the view that the droppings of animals whose meat is not permissible to eat are impure have differed regarding the ruling when a garment or body is affected by droppings about which there is doubt whether they are from an animal whose meat is permissible to eat or not. There are two opinions: ruling them impure or ruling them pure.

The more correct opinion is to rule them pure, because the fundamental principle concerning substances is purity. Imam Ahmad explicitly permitted the droppings whose source is unknown.