In Revelation 22:1–5, talking about the New Jerusalem, John writes, "Then the angel showed me the river of the water of life, bright as crystal, flowing from the throne of God and of the Lamb through the middle of the street of the city; also, on either side of the river, the tree of life with its twelve kinds of fruit, yielding its fruit each month. The leaves of the tree were for the healing of the nations. No longer will there be anything accursed, but the throne of God and of the Lamb will be in it, and his servants will worship him. They will see his face, and his name will be on their foreheads. And night will be no more. They will need no light of lamp or sun, for the Lord God will be their light, and they will reign forever and ever."
In the New Jerusalem, why will the nations need healing?
So, this tree of life, which is also found in the garden of Eden, will be found in the New Jerusalem and its leaves will heal the nations. Why would the nations need healing? We know this healing is not of physical wounds as warfare will have ceased. Nor is it for illness or disease or any kind of pain (Revelation 21:4). The healing could mean from strife and discord and conflict as nothing there will be "accursed."
The other, more likely interpretation is that the leaves of this tree provide and promote health, rather than curing disease or injury. The Greek term used to describe their effect is therapeian. This is from the same root word used to create the English term therapy. Therapy does not actually heal, but it promotes good health and wellness. In the same way, then, the leaves of this tree are for the continued health of the nations. In English, "healing" is a possible meaning of this word, but it's much clumsier than the original Greek.
Everything in God's New Jerusalem will be blessed and in accord with His desires. No sin exists, perfect government exists, and the ability to worship God together exists. There will be complete peace—with God and with each other. Part of God's means to promote this perfection, either literally or symbolically, are the leaves of this healing tree.
What does the Bible say about the new heavens and the new earth?
What does the Bible say about the New Jerusalem?
The river of life – What is it?
Will heaven have literal streets of gold?
Why will there be walls around the New Jerusalem?
Truth about Eternity