Whoever, out of ignorance, denies that fornication—or any other manifest prohibition upon which there is unanimous agreement—is forbidden is to be informed of this. But if he is someone who could not be ignorant of it, he has disbelieved.
His statement, “Whoever, out of ignorance, denies that fornication—or any other manifest prohibition upon which there is unanimous agreement—is forbidden is to be informed of this. But if he is someone who could not be ignorant of it, he has disbelieved”: if he denies the prohibition of fornication by saying, “Fornication is lawful”—and we seek Allah’s protection—then it must be considered whether he is ignorant. If he is ignorant, he has not disbelieved; but if he is knowledgeable, he has disbelieved. Yet by what criterion do we determine whether he is knowledgeable or ignorant? If he was raised among Muslims, this indicates that he is knowledgeable, and thus he has disbelieved. But if he has only recently embraced Islam, or was raised in a remote desert region—for the desert dwellers and Bedouins are far removed from knowledge of the ordinances that Allah revealed to His Messenger, may Allah’s peace and blessings be upon him—then he does not disbelieve if he denies its prohibition and claims ignorance. However, if he is taught and then persists, he has disbelieved.
His statement, “or any other manifest prohibition upon which there is unanimous agreement,” includes, for example, the prohibition of usury. Thus, if someone says, “Usury is lawful,” this does not refer to denying the prohibition of a particular type concerning which the scholars differ. For example, exchanging one apple for two is usury according to al-Shafi‘i, but it is not usury according to Imam Ahmad. Thus, if the followers of Imam Ahmad say that one apple for two is lawful, they have not disbelieved. Rather, what the author means is that if someone denies the prohibition of usury altogether, he is undoubtedly a disbeliever, because the prohibition of usury is explicitly stated in the Quran: “Allah has permitted trade and forbidden usury.” [al-Baqarah: 275] Denying its prohibition is therefore to reject Allah’s word as false, and thus he is a disbeliever.
The prohibition of usury in general is established by definitive consensus,