the Sunan collections it is reported that the Prophet, may Allah bless him and grant him peace, said:

“Whoever combines two sales in one transaction is entitled to the lower of the two prices; otherwise, it is usury.”

An example is their bringing in an intermediary to give the transaction a semblance of lawfulness. One of them buys from him something he has no interest in, so that the recipient of usury can sell it to the payer of usury; the payer then sells it back to the intermediary for a lower price. It is established that the Prophet, may Allah bless him and grant him peace, cursed the recipient of usury, its payer, its witness, and its recorder. He also “cursed the man who marries a divorced woman to make her lawful for her former husband, and the man for whose benefit this is done.”

Another example is their combining usury with a form of loan. It is established that the Prophet, may Allah bless him and grant him peace, said:

“It is not lawful to combine a loan with a sale, stipulate two conditions in a sale, profit from something for which one has not assumed liability, or sell what one does not have.”

Furthermore, “the Prophet, may Allah bless him and grant him peace, prohibited muzābanah and muhāqalah”—purchasing fruit and grain on the basis of estimated quantities. Likewise, he prohibited selling a heap of food whose volume is unknown in exchange for a specified quantity of food. This is because, where equality is required, not knowing that the quantities are equal is equivalent to knowing that they are unequal. Estimation does not establish the actual quantity by measure; it is merely approximation and conjecture. The imams agree on this.

Yet it is established that he granted a concession for ‘arāyā sales, allowing those concerned to purchase the fresh dates for their estimated equivalent in dried dates. Thus, in this instance, a commodity subject to the rules of usury may be purchased on the basis of its estimated quantity. Where there was a need, he allowed estimation to take the place of measurement. This is part of the perfection of the Sharia’s merits. Likewise, he allowed estimation to take the place of measurement when determining the zakat due and dividing crops. He would estimate people’s fruit crops to calculate their zakat, and ‘Abd Allāh ibn Rawāhah would divide the crops with the people of Khaybar by estimation, at the command of the Prophet