God commanded man to not eat of the tree of knowledge of good and evil and even told him the consequences of his actions, should he disobey God. When the devil beguiled Eve into disobeying God, he directly contradicted what God said.
God said, “You shall surely die.” (Genesis 2:17)
The Devil lied, “You shall not surely die.” (Genesis 3:4)
When diametrically opposing, contradictory, statements are presented for one to choose, only one of it could be the absolute truth and the other an absolute lie. When Adam and Eve chose to disobey God, they were in essence stating that the devil was telling the truth, and that God was a liar. In other words, they chose to not believe that God was telling them the truth, and the sin of world (even today) is unbelief in God (John 16:9).
Points to ponder:
Let us not be beguiled into believing the father of lies (the devil) and in essence make God a liar. Let us not be guilty of the sin of the world and not believe in him, for though we are in the world, we are not of it, just as Christ was not of it (John 17:14,16).
Genesis 2:17 (KJV)
16 And the Lord God commanded the man, saying, Of every tree of the garden thou mayest freely eat:
17 But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die.
Genesis 3:4 (KJV)
4 And the serpent said unto the woman, Ye shall not surely die:
John 17:12-16 (KJV)
13 And now come I to thee; and these things I speak in the world, that they might have my joy fulfilled in themselves.
14 I have given them thy word; and the world hath hated them, because they are not of the world, even as I am not of the world.
15 I pray not that thou shouldest take them out of the world, but that thou shouldest keep them from the evil.
16 They are not of the world, even as I am not of the world.