In Revelation 22:18-19 it says “I testify to everyone who hears the words of the prophecy of this book: if anyone adds to them, God will add to him the plagues which are written in this book; and if any man shall take away from the words of the book of this prophecy, God shall take away his part out of the book of life, and out of the holy city, and from the things which are written in this book.
What does this passage mean if our salvation is supposed to be secure?
John was giving a warning to anyone who tries to re-write the book of Revelation by either adding to it or taking away from it.
Notice John didn’t say “the Lamb’s Book of Life” which is where the names of the Church are written. These names were written before the foundation of the world and cannot be changed.
Since eternal security is a blessing given only to the Church we have nothing to worry about.