Among the impurities that he lists, the author says: “Human vomit … yet a small amount is excused.”

I say: The author has cited no evidence for this ruling, apart from his claim that there is consensus on its impurity. That claim, however, is untenable, for Ibn Ḥazm explicitly declared a Muslim’s vomit to be pure; see al-Muḥallā, 1 / 183. The same position is held by Imām al-Shawkānī in al-Durar al-Bahiyya and by Ṣiddīq Ḥasan Khān in his commentary, 1 / 18–20, where neither of them lists human vomit among the impurities at all—and that is the correct view. They further observe that the question of its impurity is disputed and give precedence to purity, saying:

“The default ruling is purity, and it is not set aside except by sound evidence that is unopposed by proof of equal or superior weight.”

Al-Shawkānī makes a similar statement in al-Sayl al-Jarrār, 1 / 43.

This very principle is one upon which the author himself relies in other matters, such as his ruling on the purity of the urine of animals whose flesh is lawful to eat