1. Rolling over a debt when the debtor is insolvent. This was the very root of usury in the pre-Islamic jāhiliyyah: a man would be owed a deferred sum by another, and when the term fell due he would say, “Will you pay, or shall I increase the amount?” If the debtor paid, the matter ended; if not, the creditor would prolong the term and add an increment to the principal, so that the debt snowballed in the debtor’s account. Allah forbade this, saying, “And if the debtor is in hardship, then let him have respite until a time of ease” (Q 2:280). Thus, when a debt matures and the debtor lacks the means, it is impermissible to roll the debt over; rather, he must be granted a delay. If he is solvent, he must settle what he owes. In neither case is there any ground for increasing the debt—whether the debtor is prosperous or in straits.

2. The second kind of riba al-nasiʾah arises in the sale of two commodities that share the causal factor of riba al-faḍl when the delivery of both, or of either one, is deferred—such as exchanging gold for gold, silver for silver, wheat for wheat, barley for barley, dates for dates, or salt for salt. The same applies to selling any of these items for its own kind on credit. Whatever else shares their effective cause follows the same ruling, as will be explained shortly.

Explanation of riba al-faḍl

Riba al-faḍl is derived from faḍl, meaning “surplus,” and denotes an excess in one of the two counter-values. The Lawgiver has expressly forbidden it in six items: gold, silver, wheat, barley, dates, and salt. When any of these is exchanged for the same species, any disparity between the two amounts is unequivocally prohibited, according to the marfūʿ ḥadith of ʿUbādah ibn al-Ṣāmit in which the Prophet said, “Gold for gold, silver for silver, wheat for wheat, barley…"