Is buying a house in installments permissible if it is done by the bank establishing a company with the client and a third partner, where the company buys the property and the bank pays its price, then the bank sells its share in the company to the client so that the client becomes its owner, with the option to pay the remaining amount in a single payment or through Tawarruq after ten years?

The role of the third partner is not clear, nor is the questioner's intent in stating: "the client can pay the remaining debt in a lump sum, or use tawarruq to pay it off." The described scenario resembles a diminishing musharakah (partnership), which is a partnership where one of the partners promises the other to buy all or part of his share through a contract they establish when the sale is intended. Resolutions on this matter have been issued, specifically Resolution No. (30231) from the Islamic Fiqh Academy and Standard No. (12) from the Accounting and Auditing Organization for Islamic Financial Institutions (AAOIFI), which state:

- Diminishing Musharakah: A new transaction that involves a partnership between two parties in an income-generating project, where one party undertakes to gradually purchase the other party's share. - Basis of Diminishing Musharakah: It is the contract concluded by the two parties, in which each contributes a share to the company's capital, specifying how profits are distributed and losses are borne in proportion to their shares. - Diminishing Musharakah is characterized by a binding promise from only one of the parties to acquire the other party's share, provided that the other party has the option to conclude sale contracts when acquiring each part. - It is permissible for one of the partnership parties to lease the share of his partner for a known rent and for a specified period, and each remains responsible for basic maintenance in proportion to their share. - Diminishing Musharakah is permissible if it adheres to the general provisions of partnerships and observes the following controls: - Not committing to purchase one party's share from the other party at the same value as the share at the time of establishing the company, but rather at the market value on the day of sale, or at an agreed-upon value. - Not stipulating that one party bears insurance or maintenance expenses; instead, these should be borne by the partnership pool in proportion to the shares. - Specifying the profits of the partnership parties as common ratios; it is not permissible to stipulate a fixed amount or a percentage of the contribution amount. - Separation between contracts and obligations related to the partnership. - Prohibiting a clause that grants either party the right to reclaim their contributed share. - The general provisions of partnerships, especially the provisions of Mufawadah (joint and several partnership), must apply to diminishing musharakah. - The partnership contract must not include any clause that gives either party the right to reclaim their capital contribution from the company's capital.