What does Revelation 2:23 mean?

This is part of Jesus' message to the church in Thyatira. Previously, He mentioned a woman, identified as Jezebel, which might be her real name or simply a reference to the Old Testament queen.

Centuries prior to this revelation, the prophet Elijah triumphed over Jezebel's prophets. That was a public, dramatic display of Yahweh's rightful claim to be Israel's God (1 Kings 18:20–40). As a result of Elijah's victory over Jezebel's prophets, all Israel knew that Yahweh was God. First Kings 18:39 reports: "And when all the people saw it, they fell on their faces and said, 'The LORD, he is God; the LORD, he is God.'" Following this shout of triumph, at Elijah's command, the people seized Jezebel's prophets, and then, at the brook Kishon, those false prophets were executed (1 Kings 18:40).

Here, Jesus promises to strike Jezebel's followers dead. In a parallel to the corrupt followers of the Old Testament Jezebel, the followers of Thyatira's Jezebel will taste death at the hands of God. Note, crucially, there is no command, or even a hint, that any Christian is meant to enact this sentence themselves. The threat is coming from Jesus, to be carried out in His own time and manner.

As a result, all the churches will be reminded that Jesus knows the mind and heart, and repays each person according to his works. Believers are not saved through good deeds, nor do they "earn" salvation (Titus 3:5), but their deeds influence the eternal rewards they stand to gain in Heaven (1 Corinthians 3:14). Sinners who refuse to repent will prove the truth of Romans 6:23: "For the wages of sin is death."