What is the ruling on a merchant selling gold rings designated for men, with certainty that the buyer will wear them?

Selling gold rings to men is forbidden for the seller if he knows or strongly suspects that the buyer will wear them, because gold is forbidden for the males of this Ummah. By this sale, the seller assists in sin, and Allah the Almighty has prohibited cooperation in sin and aggression, as He says: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression." (Al-Ma'idah/2). It is also not permissible for a jeweler to manufacture gold rings for men.