This is because interest, in its basic form, is resorted to only by someone in need. A person of means would not take a thousand now in return for twelve hundred payable later unless he needed that thousand. Only someone who needs the money takes it in return for an equivalent sum plus an increase payable later. That increase therefore constitutes an injustice against the needy person. Gambling is different: the person wronged in it is neither destitute nor in need of entering the transaction. Some forms of it may involve no injustice if the item sold subsequently turns out to have the qualities both parties expected. Interest, however, involves a definite injustice against someone in need.

For this reason, interest is the opposite of charity. Allah has not left the wealthy without obliging them to give to the poor, for the welfare of rich and poor alike, in both their religious and worldly affairs, cannot be fully secured otherwise. If the wealthy man then charges the poor man interest, it is like the case of someone who is owed a debt but is denied repayment and subjected to a further injustice, even though he needs the money owed to him. This is among the gravest forms of injustice. Because of its enormity, the Prophet, may Allah bless him and grant him peace, cursed the one who consumes interest—that is, the recipient—and the one who pays it—that is, the needy person who pays the additional amount—as well as its two witnesses and its scribe, because they assist in it.

The Prophet, may Allah bless him and grant him peace, also prohibited certain things whose harmfulness is less apparent because they lead to definite harm, just as he prohibited a small quantity of wine because it invites consumption of a larger quantity. One example is interest through unequal exchange. The wisdom behind its prohibition may not be apparent, since a rational person would not sell one dirham for two unless their qualities differed: for example, the single dirham might be intact while the two dirhams are broken, or the single dirham might consist of worked silver or belong to a readily accepted currency, and so forth. Thus, the wisdom behind its prohibition was not apparent to Ibn ‘Abbās and Mu‘āwiyah