What is the ruling on buying building materials with cash and supplying them to contracting companies in installments, and what is the ruling on the money previously acquired, and is it possible to pay an upfront amount to merchants to settle this transaction?

Scholars have differed regarding the ruling on supply contracts. The Islamic Fiqh Academy has issued a resolution stating their impermissibility if the promise is binding and the price is not paid in advance. However, some contemporary scholars permit the contract, asserting that the perceived prohibitions, such as selling what one does not own and deferring both counter-values, are inconsequential. As for the money earned by the questioner before becoming aware of the impermissibility, the preponderant opinion is that it is permissible for him.