What is the ruling on a contract to purchase a house in installments from a German real estate company, where financing is obligatorily provided by an insurance company, through a four-party contract that brings together the real estate company, the financing insurance company, the contractor, and the beneficiary, with a fixed and known profit margin, a fixed installment, and a known repayment period, with the insurance company overseeing the construction phases, and without any increase in the installment in case of late payment? Is this sale permissible or does it involve usury (riba)?

The manufacturing contract (Istisna'a) between you and the insurance company is permissible under two conditions: clarity regarding the type, kind, quantity, and desired specifications of the manufactured item, and the determination of the deadline. It is permissible for the entire price to be deferred or paid in installments, and it may include a penalty clause. However, if the contract involves the company paying for the materials and labor costs and then collecting an increased amount, it constitutes a usurious loan (riba) and is not permissible except in cases of necessity. The difference between the two is that Istisna'a is an agreement for the company to undertake the construction of a building with specified characteristics and deliver it by a known deadline for a known price, whereas in a loan, the company pays for the goods and labor without assuming responsibility for the construction.