What is the ruling on operating a gold processing business with a jeweler based on grams of gold, and benefiting from a monthly profit shared with him, knowing that this field does not incur losses and achieves a steady monthly profit, but it was agreed that the monthly profit is not fixed, varying by increase or decrease?

If the agreement between you and the goldsmith is that you pay him gold for him to fashion and sell, or merely sell, on the condition that you give him a percentage of the profit, this is not permissible according to the majority of scholars due to the uncertainty (Jahālah) in the wage. Some scholars have permitted the wage to be a percentage, such as giving a tailor a piece of cloth to cut into shirts and sell, with half of the profit going to the tailor, provided that the percentage of the profit is specified when the contract is renewed monthly, and that either party has the right to terminate the contract after its expiration. However, if the contract duration is long or the percentage is not determined from the outset, it is impermissible by agreement.