God said to Adam that because he had listened to his wife and ate fruit from the tree about which God had commanded him not to eat; that the ground is cursed; and because of  painful toil, he would eat food from it all the days of his life.

        God said the ground would produce thorns and thistles  and Adam would eat the plants of the field and by the sweat of his brow he would eat his food until he return to the ground. Since Adam was taken from the dust he will return to dust.