This same phrase had appeared in Revelation 22:2 and Revelation 22:14 (also in Revelation 2:7). It is a clear reference to the tree of life that stood in the Garden of Eden (Genesis 2:9), from which, were a man to eat of its life-giving fruit, he would live forever (Genesis 3:22). As the redeemed child of God is destined to inherit the New Jerusalem with its abundant life-giving trees (Revelation 22:2), taking away from God’s Word will deny access to that tree with its life-giving fruit.
19 and if anyone takes away from the words of the book of this prophecy, God will take away his share in the tree of life and in the holy city, which are described in this book.