What does 1 Corinthians 15:52 mean?

"Behold!" Paul has declared. He is revealing the mystery of how corrupt, temporary human bodies can possibly enter eternity with God. The short answer is they can't, even if those bodies belong to believers who are guaranteed salvation through faith in Christ. Instead, every born-again Christian will be transformed from their natural body to their glorified heavenly body. This will all happen when Christ returns for His people, as He said he would in John 14:2–3. Not only will the dead be resurrected with transformed, glorified bodies, but those believers who have not died when He returns will be transformed, as well.

The change will be instant: "in the twinkling of an eye." This is translated from the Greek phrase en rhipē opthalmou, which most literally means "flicking the eye" and was the ancient reference to "the blink of an eye." This depicts not only the rapid movement of the eyelid, but the speed at which the eye turns from one direction to another. The underlying point is something so rapid, so instantaneous, that it defies measurement. Paul says it will be accompanied by the blast of a trumpet, something that often accompanied the appearance of God in Scripture. This is the final trumpet blast, because God's people will never be separated from Him again.

Paul, speaking of the living, says "we shall be changed." This should not be taken to mean Paul necessarily expected to be alive when Christ returns. For example, he used "we / us" language to included himself among those who will be resurrected after death in 1 Corinthians 6:14. Paul did not claim to know specifically when Christ would return (Matthew 24:36).

This passage lines up almost exactly with what Paul wrote in 1 Thessalonians 4:15–17. Many churches and denominations describe this event as the rapture of the church.