Revelation 22:20 Meaning

18For 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:

19And 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.

20He which testifieth these things saith, Surely I come quickly. Amen. Even so, come, Lord Jesus.

21The grace of our Lord Jesus Christ be with you all. Amen.