Satan is always casting doubt on God’s word. The first words out of his mouth accuse God of lying. Satan lied to Eve and charged God with keeping her back from becoming a god, and so she fell.
Genesis Chapter 3
1 Now the serpent was more subtle than any beast of the field which the LORD God had made. And he said unto the woman, Yea, hath God said, Ye shall not eat of every tree of the garden?
2 And the woman said unto the serpent, We may eat of the fruit of the trees of the garden:
3 But of the fruit of the tree which is in the midst of the garden, God hath said, Ye shall not eat of it, neither shall ye touch it, lest ye die.
4 And the serpent said unto the woman, Ye shall not surely die:
5 For God doth know that in the day ye eat thereof, then your eyes shall be opened, and ye shall be as gods, knowing good and evil.
And who is the serpent…
Revelation 12:9 “And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him.”
2 Cor 11:3 “But I fear, lest by any means, as the serpent beguiled Eve through his subtlety, so your minds should be corrupted from the simplicity that is in Christ.”