Is it permissible to trade gold via Forex, especially with the 40-hour delay in receiving the price due to banking procedures, and the assurance that there are no usurious or non-usurious interests, with a small percentage taken for buying and selling, and does this differ from trading through a bank?

What the brokerage firm takes as a fixed commission for buying and selling services is permissible. However, the problem lies in not receiving the price immediately, whether the delay is intentional or due to banking procedures. Selling gold for silver or currencies requires immediate hand-to-hand exchange at the time of the contract. The proof for this is the hadith (definition) of Abu al-Minhal regarding currency exchange, and the Prophet's (peace be upon him) prohibition of selling gold for gold except equally, and his command that we buy silver for gold as we wish, with the condition of hand-to-hand exchange.

If the brokerage firm receives the price at the time of sale and then delays sending it, there is no harm, because it is an agent for the seller and the possession has occurred. Contracts made over the phone are valid if possession takes place immediately after the conversation ends. However, if the sale is fictitious, it is prohibited usury (riba).

This field involves Sharia (definition) risks such as usury (riba), ambiguity (gharar (definition)), and gambling, so it is advisable to avoid it.