The answer to your good question is found in Genesis 3:22, but we will read verses 22-24: “Then the LORD God said, ‘Behold, THE MAN HAS BECOME AS ONE OF US, TO KNOW GOOD AND EVIL. And now, LEST HE PUT OUT HIS HAND AND ALSO TAKE OF THE TREE OF LIFE, and eat, and live forever’—therefore the LORD God sent him out of the garden of Eden to till the ground from which he was taken. So he drove out the man; and He placed cherubim at the east of the garden of Eden, and a flaming sword which turned every way, to guard the way to the tree of life” (NKJV).

It is clear from verse 22 that “the man” (Adam) had already eaten of the tree of the knowledge of good and evil, which means THE DAMAGE HAD ALREADY BEEN DONE! God had told Adam, “Of every tree of the garden you may freely eat; but of the tree of the knowledge of good and evil you shall not eat, for in the day that you eat of it you shall surely die” (Genesis 2:16-17). We know from Genesis 3:6 that Adam did indeed eat of the forbidden fruit, “So the woman…took of its fruit and ate. She also gave to her husband with her, and HE ATE.” The eating of that tree brought death to Adam and to the whole human race, as we see in Romans 5:12, “Therefore, just as through one man sin entered the world, and death through sin, and thus death spread to all men, because all sinned.” It also gave them “the knowledge of good and evil”; in other words, they lost their innocence and became aware of sin. We believe they gained a CONSCIENCE that day, an “inward voice” that would tell them whether they were doing “good or evil.” Romans 2:15 speaks to this, “Who show the work of the law written in their hearts, their CONSCIENCE ALSO BEARING WITNESS, and between themselves their thoughts ACCUSING OR ELSE EXCUSING THEM.” So, with Adam and Eve having already eaten of the forbidden tree, there was no need to guard the tree of the knowledge of good and evil.

It would seem that Adam and Eve had NOT yet eaten of the tree of life, for if they had, they would LIVE FOREVER. This means they would have gained IMMORTALITY; their BODIES WOULD NEVER DIE. There are two reasons that God placed angelic guards to guard the tree of life:

1) If Adam and Eve ate of the tree of life and gained immortality, they would have LIVED FOREVER IN A FALLEN, SINFUL CONDITION. This means they would have had been “slaves to sin” and lived miserable lives forever and ever. Though they had gained the “knowledge of good and evil,” they also gained a sinful nature that brought them into bondage to sin. Jesus said in John 8:34, “Most assuredly, I say to you, whoever commits sin is a slave of sin.” I would encourage you to read Romans 7:13-24 where the Apostle Paul speaks of the fallen, sinful nature of man (which he refers to as “sin that dwells in me” in verses 17 & 20) and how it brings people “into captivity to the law of sin” (verse 23).

2) If Adam and Eve ate of the tree of life and gained immortality, GOD’S WORD WOULD HAVE FAILED. We read in Genesis 2:17 that God had decreed, “In the day that you eat of it you shall surely die.” This “death sentence” included “spiritual death” and “physical death.” The very moment they ate of the forbidden fruit they DIED SPIRITUALLY (see Ephesians 2:1) and they BEGAN TO DIE PHYSICALLY. If they would have eaten of the tree of life they would not have died physically and God’s Word would have proven to be wrong. Of course, this could never happen and to prevent that from happening, God placed cherubim in the garden to “guard the way to the tree of life.” (336.3) (DO)