20 – It is related from ʿImrān ibn Ḥuṣayn (may Allah be pleased with him) that “the Prophet ﷺ and his Companions performed ablution with water taken from the leather water-skin of a polytheist woman.” Agreed upon, within a longer narration. (1)

—

Vocabulary of the ḥadith
– mazādah: a large leather water-skin used for storing and carrying water. According to Abū ʿUbayd, it is normally fashioned from two hides with a third inserted between them so that it can hold a greater volume.
– mushrikah (polytheist woman): In Islamic law, a mushrik is one who assigns a partner to Allah. If this association concerns Allah’s own acts, it is shirk in Lordship; if it concerns the servant’s acts, it is shirk in divinity and worship.

Points inferred from the ḥadith
1 – It is permissible to use the hide of a dead animal after tanning, even for liquids. The Prophet’s ﷺ ablution from the mazādah constitutes tacit approval of such use.
2 – The water contained in a tanned hide taken from an animal that died unlawfully remains pure. Although the slaughter of a polytheist renders the animal carrion—unlawful and impure—tanning removes the filth from its hide and purifies it.
3 – Carrion (maytah) is an animal that dies naturally or is killed in an unauthorized manner; when the slaughter is carried out by a polytheist, it likewise falls under the category of unlawful killing.
4 – The vessels of unbelievers whose actual state is unknown are judged pure, for the default ruling is purity, and that presumption is not overturned by mere doubt arising from their use of the vessels.

As for Allah’s words, “Indeed the polytheists are impure” (Qur’an 9:28), the impurity intended here is doctrinal, not physical.