Is the transaction of buying gold bars online, as described in the question, considered permissible (halal) or a form of riba al-nasi’ah (usury of delay), given that it is the only safe method for purchasing fabricated bars?

The aforementioned transaction is invalid due to the non-fulfillment of the condition of immediate possession (taqabud), neither actually nor constructively. The lack of assurance for purchasing except through these companies is not an excuse, as permissible alternatives are available. The purchase of gold with currencies is considered a currency exchange (sarf), and it requires immediate possession at the same session, based on the Prophet's (PBUH) saying: "If it is hand to hand, then there is no harm; but if it is deferred, then it is not permissible," and his saying: "What is hand to hand has no harm, but what is deferred is usury (riba)." Paper currencies are annexed to gold and silver in Sharia rulings; zakat is obligatory on them, and riba an-nasa' (usury of delay) and riba al-fadl (usury of excess) are forbidden in them. Therefore, it is not permissible to purchase gold bars in the manner described, and whoever guards himself against doubtful matters has indeed cleared himself in respect to his religion and honor.