but forbidden and impure for the latter. Turning wine into vinegar is a similar case: since doing so is prohibited, deliberately undertaking it does not make the resulting vinegar lawful or pure, just as slaughtering an animal in a manner not prescribed by Islamic law does not make its meat lawful and pure.

What we have related from ʿUmar ibn al-Khattāb is the authoritative basis in this matter: whenever it is known that the owner deliberately set out to turn the wine into vinegar, it must not be purchased from him. If that is not known, it may be purchased from him, because the owner of wine is ordinarily unwilling to turn it into vinegar. And Allah knows best.