Is it permissible to agree to lend a sum of money on the condition of receiving a percentage of the profits from the project that will be completed with this sum, provided that everyone bears the loss if it occurs? And what is the correct formula for the agreement if this is not permissible?

Every loan that draws a benefit for the lender is usury (riba). It is not permissible for a loan contract to be accompanied by a condition that benefits the lender. If the owner of the capital wishes to benefit from his money through the borrower, there is no way to do so except through a partnership (sharika) contract or a Mudaraba contract.

A permissible Mudaraba is a contract between two parties: one provides the capital, and the other trades with it, on the condition that the worker receives a widespread share of the profit. If a loss occurs, each of them loses what they contributed. One of the conditions for the validity of Mudaraba is that the investor's profit should not be a percentage of the capital, but rather a widespread percentage of the profit. In Mudaraba, both parties do not jointly bear the loss of the capital; rather, the owner of the capital alone bears it, and the Mudarib (worker) loses his effort. If the owner of the capital stipulates that the Mudarib share in the loss, the condition is void, but the contract remains valid.