Revelation 22:18 in the King James Version
For I testify unto every man that heareth the words of the prophecy of this book, If any man shall add unto these things, God shall add unto him the plagues that are written in this book:
Context
17 The Spirit and the bride say, “Come!” He who hears, let him say, “Come!” He who is thirsty, let him come. He who desires, let him take the water of life freely.
18 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.
19 If anyone takes away from the words of the book of this prophecy, God will take away his part from the tree of life, and out of the holy city, which are written in this book.