What is the ruling on water collected in Roman stone tombs when rain flows into them and is used for ritual ablution?
Chapter on what purification is achieved with regarding water
Al-Mughni
Book of Purification
Primary text
The ruling favors declaring such water pure. This is because the water has been affected by countless instances of rainfall, and rain flowing over the structures purifies them. Furthermore, washing these structures is difficult, making it comparable to earth purified by the descent of rain upon it.
Supporting text
If the tombs had been washed once or twice prior, a different consideration might apply, but generally, the sheer volume of purifying rain dictates the ruling.