In Deuteronomy 17 God gave instructions to the Israelites about their future king. God said that the king must never multiply horses for himself, not multiply wives for himself, and not multiply gold for himself.
To not multiply wives and gold means God did not want the heart of the king to be drawn away from God.
To not multiply horses means that God never intended Israel to be a conquering empire. They were to be a nation of priests to the Gentile nations. The surrounding Gentile nations were to protect Israel. God’s people always had a “Gentile sponsor” — someone to support and protect them. For Abraham it was Melchizedek, for Joseph’s family (the Hebrews) it was Egypt, for Moses and the people (now called Israel) it was Jethro, For David and Solomon it was Hiram of Tyre, and for the post-exile Jews it was Babylon, Persia, Greece, and Rome (the four beasts of Daniel 7 called up out of the Gentile sea to protect God’s people). Each time a beast went bad, God replaced it.
The Roman beast protected God’s people (now called Christians) all throughout the book of Acts. It was only the apostate Jews who wanted to destroy the Church, and the Romans always protected the Church. But after the events of Acts, the Roman beast went bad and turned on the Church — so God killed it.
The first century apostate Jews worshipped the religion of power. They wanted their Messiah to come with a sword and establish a Jewish empire. Jesus offered a religion of righteousness and self-sacrifice, but the apostate Jews rebelled against that and said, “We have no king but Caesar!” The Jewish leadership caused the people to worship the Roman beast — power religion.
We read about this in Revelation 13. The Land Beast (the Herods and the High Priesthood — two horns) caused all the people on the land (Israel) to worship the Sea Beast (the power of the Roman empire). The Land Beast caused all the people to put the mark of the Sea Beast on their foreheads — 666. That’s in direct contrast to the mark of God put on the foreheads of the faithful Jews in Revelation 7. No one could buy or sell without the mark. Buying and selling refers to worship, which is why Jesus says, “I counsel you to buy from Me gold…” (Revelation 3:18).
Solomon, at the peak of his career, did exactly as God intended for Israel. He built the temple and people from the surrounding nations came to Israel to see the glory of God and to learn from the kingdom of priests. But, Solomon went bad and began to worship power religion. We can read of his downfall in 1 Kings.
In 1 Kings chapters 10 & 11 we read that Solomon multiplied for himself horses, wives, and gold — exactly what he was not supposed to do as king. And we know he became a harsh king because when his son, Rehoboam, took power, the people asked for a more lenient rule (1 Kings 12).
When we read about Solomon multiplying gold (1 Kings 10:14), the bible says that he had 666 talents of gold coming to him each year. There’s more to that number than just this, but anyone “with understanding” reading the book of Revelation in the first century would have seen that the number 666 directly tied the Jewish worship of power religion to the fall of Solomon and his worship of power religion.
There is no need to go outside the bible to understand the number 666 or any of the other symbols in Revelation. 666 does not refer to Barak Obama, George W Bush, three W’s, or any of that stuff. It can all be understood by looking back into the Old Testament.
*This explanation of 666 is derived from James B Jordan’s teaching on the book of Revelation, which you can buy here.