What is the ruling on dealing with gold merchants who follow a system where the quantity of gold withdrawn is determined by the change in its price after one year, and how is the zakat on this gold paid?

It is not permissible to sell gold and silver except with immediate, hand-to-hand exchange in the contracting session. The sale must be decisive and without hesitation; therefore, delaying possession is not allowed. For a salam (forward) sale, it is stipulated that the commodity being sold must be known in terms of its description, quantity, and delivery date. However, a salam sale is not valid for gold, silver, and currencies due to the requirement of immediate possession for them.