In the PDF ‘Tahaarat Made Easy’ it says:
“The water from which man, (Muslim or kafir, in need of Ghusal or in a condition of haiz, young or
old) or a horse or any animal (whose meat is Halaal) drank, then the leftover water will be impure.”
Could you explain what is meant by impure here? Does it mean unclean / najas? If so, why is this unclean? Could you please explain the rule for this impurity spreading when one is in a state of requiring ghusl?
Jazak Allah Khair