Sunan Ibn Majah, 519

Rapporté par Abu Sa‘id Al-Khudri : On a interrogé le Prophète au sujet des bassins d’eau situés entre La Mecque et Médine, visités par des animaux sauvages, des chiens et des ânes, et sur leur utilisation pour la purification. Il a dit : "Ce qu’ils (les animaux) ont emporté dans leur ventre est pour eux, et ce qui reste est pour nous, et c’est pur

It was narrated from Abu Sa'eed Al-Khudri that:The Prophet was asked about the water basins located between Makkah and Al-Madinah, which were visited by wild animals, dogs and donkeys, and about using them for means of purification. He said: "Whatever they (the animals) have carried in their bellies is for them, and whatever is left over is for us, and is pure