2. Ribā al-nasīʾa: this is the sale of a measured edible for another measured edible, or a weighed edible for another weighed edible—even when the two are not of the same genus—on deferred payment. Hence it is forbidden to sell one of them for the other on credit, or for both objects to remain undelivered in the very session in which the contract is concluded. Such a transaction is unlawful and void by the consensus of the scholars, a consensus grounded in clear and sound textual evidence.

3. Ribā al-qarḍ: this occurs when someone lends an item that may lawfully be the subject of a loan and stipulates, in return, a benefit—such as allowing the lender to live in the borrower’s house, ride his mount, or have the loan repaid with something superior in quality, and the like. These, then, are the forms of ribā that Allah the Exalted and His Messenger ﷺ have prohibited.

Ibn al-Qayyim classified ribā into two kinds, the hidden and the manifest:

• The hidden form is prohibited because it is a means that leads to the manifest form; its ruling comes under the principle of blocking the avenues that lead to forbidden ends. This is ribā al-faḍl, for if a dirham is exchanged for two dirhams the deal progresses toward deferred profit, which is the very cause of ribā al-nasīʾa. In His wisdom Allah closed this door, and that wisdom is plain to see.

• The manifest form is ribā al-nasīʾa itself, the practice common in the Days of Ignorance. It is usually undertaken only by someone in need; the creditor’s wealth thus grows at the expense of the destitute without bringing him any real benefit, until debt crushes him. Out of mercy for His servants, Allah forbade it.

Ribā in the pre-Islamic era: al-Jaṣṣāṣ writes in his Tafsīr that the ribā known and practiced by the Arabs was to lend dirhams or dīnārs for a set term with an excess stipulated above the principal, according to whatever amount the two parties agreed upon. This was the custom that prevailed among them.

Concerning those who do this, the Almighty says: “O you who believe! Fear Allah and give up what remains of interest, if you are true believers. But if you do not, then be informed of a war from Allah and His Messenger. Yet if you repent, you may have your principals—you will neither wrong nor be wronged.” (al-Baqarah 2:278–279)

This explicit text shows that the creditor is entitled only to his original capital, with no increase whatsoever, for when the debt of an insolvent person fell due they would say to him: