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.Revelation 22:1-2 NIV
In the second chapter of Genesis, God planted a garden in Eden. And he placed Adam there to care for it. In the midst of the garden was the tree of life. But in the third chapter, Adam and Eve sinned by eating from the forbidden tree. And, a result, they were cast out of the garden to prevent their eating from the tree of life. A guard was then placed at the entrance to the garden, and this tree is never mentioned again. Until Revelation.
As a part of the letter to the church at Ephesus (Rev 2:1-7), Jesus told them that those who conquer will be given the right to eat from the tree of life in God’s paradise. And now, at the end of the Bible, access is once again restored. What was lost when paradise (Eden) was closed, is restored in the Holy City (Rev. 21:2, 10), the new paradise of God (Rev. 1:7).
Blessed are those who wash their robes, so that they may have the right to the tree of life and that they may enter the city by the gates. – Revelation 22:14