"And out of the ground the Lord God made to spring up every tree that is pleasant to the sight and good for food. The tree of life was in the midst of the garden, and the tree of the knowledge of good and evil.

After Adam and Eve ate from the Tree of the Knowledge of Good and Evil (which God had forbidden).   In Genesis 3:22-24, God says:

"Behold, the man has become like one of us in knowing good and evil. Now, lest he reach out his hand and take also of the tree of life and eat, and live forever—" .  God then expels them from the Garden of Eden and barred them from the Tree of Life .  The Tree of Life had the power to grant eternal life, and its inaccessibility became a consequence of human disobedience.

Proverbs 3:18: "She [wisdom] is a tree of life to those who lay hold of her; those who hold her fast are called blessed."

Proverbs 11:30: "The fruit of the righteous is a tree of life, and whoever captures souls is wise."

Proverbs 13:12: "Hope deferred makes the heart sick, but a desire fulfilled is a tree of life."

Proverbs 15:4: "A gentle tongue is a tree of life, but perverseness in it breaks the spirit."

Revelation 2:7: "To the one who conquers I will grant to eat of the tree of life, which is in the paradise of God."

Revelation 22:1-2: "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 22:14: "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."