Is the fixed 3% increase on the price of a house sold in installments by a charity organization, which funds its operations through the bank and acts as an intermediary between the seller and the buyer, considered usury (riba)?

Purchasing real estate in installments occurs in two ways:

1. Usurious financing: This is when the intermediary (bank or office) finances the buyer by paying the price to the seller, then recovers the price from the buyer with a stipulated increase. This transaction is considered forbidden usury by scholarly consensus, as it is a loan with an increment.

2. Permissible installment sale: This is when the office buys the house from the seller with cash, then sells it to the buyer in installments. This is permissible under the following conditions: No increase in installments should be stipulated if the buyer delays payment. The office must genuinely purchase and take possession of the house before selling it to the buyer. It is not permissible to sell what one does not own or has not taken possession of. It is not permissible to finalize the sale contract or take a down payment from the buyer before the office has purchased and taken possession of the house.

If these conditions are met, the transaction is permissible. The sin of usurious borrowing, if committed by the office, falls upon it and does not invalidate the sale and purchase from the buyer's perspective.