What is the ruling on participating in a company that sells gold at a price higher than its market value, and pays the participant a commission (reward) for convincing others to join?

This operation is impermissible as it involves uncertainty regarding the price and contains elements of risk and gambling (qimar), which is the Gharar (ambiguity/deception) forbidden by Islamic law. Furthermore, it involves the sale of money for money with deferment (nasi’a) and the possibility of an increase. Whatever exceeds the actual value of the gold item is paid in exchange for what the company will return upon bringing ten customers. Since money has the same ruling as gold and silver, it is not permissible to sell any of it on credit (nasi’a) or for less or more than its kind, even if hand-to-hand.