Gen. 3:5 For God knows that in the day you eat of it your eyes will be opened, and you will be like God, knowing the difference between good and evil and blessing and calamity.
Satan’s temptation was that if they would eat from the tree of the knowledge of good and evil that their eyes would be opened, thus knowing good from evil, and they would be like God. Simply put, if you could just discern good from evil then you would be able to avoid the evil and do the good by your own self effort. This is at the heart of the fall and the fallen heart. God had already told them that by gift, (grace) they were created in His image to reveal Hs likeness. In other words, they were created to, contain, enjoy and reveal His presence, thus manifesting His likeness. Their responsibility was to, out of intimate love for Him, stay utterly dependent on Him in total faith. The temptation was, forsaking faith, try by self effort to become; try to get; what you already are and already have by grace in God. This dynamic is at the core all spiritual progress. We are constantly being tempted to get there, or be that, or have that apart from the simple celebration of all we already have In Christ.