The beginning of all our misery came from Satan’s first great success on the earth. It was not by means of scaring or harassing or possessing Adam and Eve. It was by deceiving them. And the deception was just this: God cannot be trusted to meet your needs and satisfy you. The serpent says only two things. One is a question that suggests God is stingy, “Has God said, ‘You shall not eat from any tree of the garden?'” The other utterance is a murderous half-truth, “You surely shall not die!” (Genesis 3:1, 4).
In his penetrating study of the Pentateuch, John Sailhammer sums up the scene like this:
The snake speaks only twice, but that is enough to offset the balance of trust and obedience between the man and the woman and their Creator. The centerpiece of the story is the question of the knowledge of the “good.” The snake implied by his questions that God was keeping this knowledge from the man and the woman (3:5), while the sense of the narratives in the first two chapters has been that God was keeping this knowledge for the man and the woman. In other words, the snake’s statements were a direct challenge to the central theme of the narratives of chapters 1 and 2; God will provide the “good” for human beings if they will only trust him and obey him.
Satan began by calling God’s goodness into question and that has been his primary strategy ever since. His aim is to subvert trust by influencing us to believe that the promise of sin is more satisfying than the promise of God. – John Piper, Future Grace