In the garden were two trees, the tree of the knowledge of good and evil and the tree of life. Adam was commanded to not eat from the tree of the knowledge of good and evil. Every other tree was given to him for food including the tree of life. When Adam sinned he was forbidden the fruit of the tree of life and dying he died. Notice what God says.
Then the LORD God said, “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 —” therefore the LORD God sent him out from the garden of Eden to work the ground from which he was taken. He drove out the man, and at the east of the garden of Eden he placed the cherubim and a flaming sword that turned every way to guard the way to the tree of life. [Genesis 3:22-24 ESV]
For Adam, now corrupted and sinful, to become like God and live forever, knowing only evil and never able to do good is a perversion of God perfect creation. For him to reach out and eat of the tree of life would mean eternal life in an eternal state of sin. God cannot allow this because of His eternal being. God separated Adam, and all those in him from the source of life, which is Himself.
For Adam and for us in him, only one sin is enough to separate all from God, who is the source of life.
In the garden the tree of life is a “type” of Christ. It is a true representation of the only means of attaining eternal life, which is Christ. Like Christ, the tree was placed in the garden and given as food to those in residence. Finally, the tree of life pointed to Christ. John tells us “in Him is life” [John 1:4 ESV] and then Jesus declared “I am the way, the truth, and the life. No one comes to the Father Except through me” [John 14:6 ESV].
Yet, Jesus declares there is an unforgivable sin, which is the rejection of the leading of the Holy Spirit by disobeying God’s direction given by the Spirit.
Therefore I tell you, every sin and blasphemy will be forgiven people, but the blasphemy against the Spirit will not be forgiven. And whoever speaks a word against the Son of Man will be forgiven, but whoever speaks against the Holy Spirit will not be forgiven, either in this age or in the age to come. [Matthew 12:31-32; see Mark 3:28-29; Luke 12:10; 1 John 5:16]
It takes only one sin to separate from God.
When Jesus died it was for all, for everyone. God now commands, He never requests, all to eat from the tree of life, which is Christ, and live. Many do. None can declare they decided to eat from the tree of life. They responded to God’s command in obedience.
Those who refuse to obey the command to eat do not get life but continue in death. Their disobedience is a hand held up to God’s face showing their hatred toward Him. Christ’s righteousness becomes a fire and they desperately try and finally succeed in escaping its heat. What changes some, preparing them for eternity with God, drives others mad with anger, hatred and bitterness.
One act of disobedience by Adam brought death to all people. One act of obedience by Christ, His sacrificial death on the cross, brought righteousness to all people. Now, one act of defiance toward the absolute authority of God results in death for the individual.
Truly, truly, I say to you, unless you eat the flesh of the Son of Man and drink his blood, you have no life in you. Whoever feeds on my flesh and drinks my blood has eternal life, and I will raise him up on the last day. For my flesh is true food, and my blood is true drink. Whoever feeds on my flesh and drinks my blood abides in me, and I in him. As the living Father sent me, and I live because of the Father, so whoever feeds on me, he also will live because of me. This is the bread that came down from heaven, not like the bread the fathers ate and died. Whoever feeds on this bread will live forever. [John 6:53-58 ESV]