The Tree of Life
The 'Tree of Life' was in 'The Garden of Eden' as was 'The Tree of Knowledge of Good and Evil'. (Genesis 2:9). The 'Tree of Life' gave Adam and Eve their immortality, but they lost their immortality when they disobeyed God. They had to leave 'The Garden' so they could not eat from the tree again (Genesis 3:22-24).
Enoch said he was shown the heavens and he saw 'The Tree of Life' (Enoch 24:9-11), "...And that tree of an agreeable smell, not one of carnal odor, there shall be no power to touch, until the period of the great judgment. When all shall be punished and consumed for ever, this shall be bestowed on the righteous and humble. The fruit of the tree shall be given to the elect. For towards the north life shall be planted in the holy place, towards the habitation of the everlasting King. Then shall they greatly rejoice and exult in the Holy One. The sweet odor shall enter into their bones; and they shall live a long life on the earth as your forefathers have lived; neither in their days shall sorrow, distress, trouble, and punishment afflict them. And I blessed the Lord of glory, the everlasting King, because He has prepared this tree for the saints, formed it, and declared that He would give it to them".
Ezekiel (47:12) said he was shown several 'Trees of Life' "...whose leaf shall not fade, neither shall the fruit thereof be consumed: it shall bring forth new fruit according to his months, because their waters they issued out of the sanctuary: and the fruit thereof shall be for meat, and the leaf thereof for medicine".
John The Revelator also stated he had a vision about 'The Tree of Life'. In Revelation 2:7 he saw Jesus who said, "...To him that overcometh will I give to eat of the tree of life, which is in the midst of the paradise of God". John then saw"In the midst of the street of it, and on either side of the river, was there the tree of life, which bare twelve manner of fruits, and yielded her fruit every month; and the leaves of the tree were for the healing of the nations; Blessed are they that do his commandments, that they may have right to the tree of life and may enter in through the gates into the city". (Revelation 22:2 and 14).
So according to Christianity, those who are in the first resurrection and/or those who hear the first call of God, will be granted access to 'The Tree of Life'. The fruit of the tree will give them immortality as it once did for Adam and Eve.
