Is it permissible, Islamically, to launch a hospital project and offer some departments for investment, whereby an investor pays a certain amount in exchange for the profits of a specific department for a limited period, without recouping the invested amount after the period ends, with the possibility of earning profits up to double or twice the amount paid?

It is permissible to offer certain hospital departments for partnership and investment. This can take two forms:

The first: The department is established with the capital of the partners, while the hospital owner manages it. The profit share for everyone must be known. The funds of this department must be separated from the rest of the hospital, and a duration for the partnership must be specified. Upon its expiration, the equipment should be appraised. It is not permissible to specify a fixed amount of money or a percentage of the capital for the investor; rather, they should have a percentage of the profit. If a partner's share is a known amount of money, the partnership becomes void.

The second: The department is partially equipped, and people's money is used to complete it. This is a partnership involving assets (عرض), and the existing equipment must be appraised as part of the hospital owner's capital.

It is not permissible to stipulate that the investor's capital cannot be retrieved, as the capital belongs to all investors. It is not permissible for a partner to invest their money in the entire hospital in exchange for a profit from a specific department, due to the presence of gharar (uncertainty) and jahalah (ignorance) therein.

There is a third form that does not fall under mudarabah (profit-sharing) or partnership. This is when the hospital equips the department and then leases it to whoever desires, with the lessee being responsible for its management and operation, and all the department's income going to them. This is permissible as a lease contract for the building and equipment.