What happened to Adam when he ate from the tree God told him not to?

He died. More precisely, the dying process began, kind of like a time bomb was set.  

This was God’s warning: But from the tree of the knowledge of good and evil you shall not eat, for in the day <Strongs #3117> that you eat from it you will surely die.” Genesis 2:17

The Hebrew word “day” in Strong’s Concordance is #3117 and the word has a wide variety of meanings – everything from the warm hours of the sun, from sunrise to sunset, a 24 hour day, or a specific period like a year or a lifetime.  It is the same way we use it today.

For example:  “In my grandfather’s day, they did not have electricity.”  You would not understand me to mean that Grandpa did not have electricity only for one 24 hour period, but instead, it meant back when he was young and vibrant – some period of time during his life.

For example:  “In the day of King Xerxes…” means the time period of his rule, not a 24-hour day.

In other places of the Bible, that exact same Hebrew word is translated: time, continually, afternoon, evening, month, months, season, space, times, yearly and many others.

We know from other Scriptures that the punishment for sin is death:  Romans 6:23:  “The wages of sin is death…” and that ALL sin Romans 3:23: “For ALL have sinned and come short of the glory of God,” therefore all of us are dying from the moment we are born.  We are all in the dying process due to the original sin of Adam.

He didn’t die physically so it stands to reason that it had to be spiritually dead (separated from God). 

God did not strike Adam dead at the exact moment of eating the fruit, as His great plan of the permission of evil (for a limited time only) would now be set in motion.  This would involve allowing Adam and Eve to populate the earth, allowing mankind to learn the consequences for sin and yearn for an ultimate reconciliation with God.  But they were removed from the Garden and would now be cursed, all of their children immediately dying at birth. 

We know that all who sin eventually die, as we are told that in Romans and other places in the Bible.  However, as you wrote, they absolutely had a spiritual separation from God, as the communication they once had was now withdrawn and they were “on their own,” so to speak.

Throughout the Old Testament, however, God found certain men and women of faith with whom He was able to intimately communicate.  Genesis 5:21: Enoch “walked with God.”  Genesis 17:1: God to Abraham – “walk before Me.”  We know heroes of faith like Noah, Moses, Joseph, Isaac, Jacob, David, Rahab and others described in Hebrews 11 had a very vibrant spiritual relationship with God (long before Jesus was ever born). 

For their faithfulness they often received physical rewards such as land, family and cattle.  They are promised a future reward in the resurrection as rulers and leaders in God’s kingdom on earth.

But there is a clue to your question in Hebrews 11:39-40:  “And these all, having obtained a good report through faith, received not the promise: God having provided some better thing for us, that they without us should not be made perfect.”

They receive a good reward, but the reward of the true Christian follower of Jesus will be better.  “They without us should not be made perfect,” tells us that their future is dependent upon the future of those true followers, also called in Scripture “the church class,” “the bride of Christ,” “the 144,000” of Revelation, and other descriptions.

This is the path we are striving for, the path that Jesus made possible.  We are assured that all who have ever died will be raised back on earth in the kingdom – the Bible speaks of the resurrection of the dead in many, many places. 

“…Thy kingdom come, Thy will be done on earth as it is done in heaven…” Matthew 6:10

  Through Christ, we now have the opportunity to “run for the prize of the heavenly calling,” as the Apostle Paul describes in Philippians 3:14.  This special class will have the reward of immortality

“Be faithful unto death and I will give you a crown of life.” Revelation 2:10

To learn more about why sin exists in the world listen to, “Is it God’s Fault We Have Evil in This World?”