All symbols in the book of Revelation are based on the Tanakh. If you know the Tanakh you know everything. Therefore 666 relates to this passage in the Tanakh,
Now the weight of gold that came to Solomon in one year was
666 talents of gold,
1 Kings 10:14
Why gold you might ask? Well, my diagram will explain it, and what the true mark of the beast is.
No, everything does not related to the Tanakh! All you are doing is repeating a teaching that has been going around, which is false. In order to come to a right conclusion, we must pay attention to the context.
Scripture states that the mark will go in/on the right hand or forehead. Unless anyone receives the mark they will not be able to buy or sell. That said, it is pretty hard to wear a piece of gold on your hand or forehead to make purchases.
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The revelation of Jesus Christ, which God gave Him to show to His bond-servants what things it behooves to take place in quickness"
The word "anastasis" translated as "revelation" is defined as " an unveiling, uncovering, revealing, a disclosure of truth, instruction, concerning divine things before unknown. Therefore, this coming mark is something that will have previously been unknown.
In John's vision he was trying to describe something that he had nothing to compare to and that because there was nothing like the technology that we have today. However, the technology for mark has been here and has been evolving. Sine 2015, employees of a certain company in Sweden have been receiving RFID chips under the skin of their hands which allows them entrance into the building, access to equipment and to be able to purchase food at the local café. This technology is also here in the US where one company is offering the RFID chip in order to make purchases in the break room.
The system which the mark will use has been in place for some time. It is the electronic crediting and debiting system that allows people to pay by the swiping of their debit or credit cards and/or via cell phone bank apps. This technology will continue to evolve to something more applicable in preparation for that coming antichrist. Very soon, we will begin to see people making purchases by the scanning of their hands, replacing the swiping of cards.
The generation that we live in is the only one where the mark could be fulfilled and that because of the system of electronic crediting and debiting (buying and selling). Paper money, checks and all other forms of buying and selling will become obsolete when that antichrist/beast proclaims himself to be God and the mark in the right hand or forehead will be the only valid method for making purchases.