What does Matthew 2:3 mean?

Matthew has described a significant event in Jerusalem. Men from the east described as "wise men" or "Magi" have arrived on a quest, likely with a large company of their own. The Greek word magoi was a general term name for those interested in dreams, astrology, and obscure wisdom. These wise men, though, knew about Israel's Scriptures. They specifically knew of about prophecies related to the Messiah, a long-awaited king who would save Israel and reign over her.

When they arrived in Jerusalem asking where the newborn king was so they could worship Him, it got Herod's attention. Herod was Israel's king-in-practice, thanks only to the authority of the occupying Romans. Herod was technically Jewish, though historical records suggest he was also an Idumean: a descendant of Esau and the Edomites, who opposed Israel. He was familiar enough with Israel's God and the old prophecies to know how influential they could be on the rest of the people.

Instead of being excited about the possibility that the Messiah, also known as the Christ, had been born in Israel, Herod was troubled. All of Jerusalem was troubled with him. We're not told exactly why others were worried as well, but Herod was known as a man willing to kill anyone to protect his own power. He'd done exactly that to his own family members. Religious and civil rulers in Jerusalem may also have been protective of their power and status, even under the rule of the Romans.