Notice that God does not merely expel Adam; he expels him to till the ground, i.e., not merely from the Garden, but to begin a life of farming. This small detail neatly ties up Adam’s story in line with the introduction, of Gen 2:4-7. Those verses, as you might recall, spoke of the “generations,” or family history, of “the heavens and the earth” and in particular of the rain (of the heavens) and the ground (of the earth). Adam is created of the earth, as his name suggests, and as he is reminded by God at 3:19 and 23. Moreover, in explaining why rain had not yet fallen (at a certain point in prehistory), it was because “there was not a man to till the ground” (2:5) and make proper use of the rain. Even in the Garden, God specifies that Adam’s role is “to dress it and to keep it.” So the expulsion “to cultivate the ground” serves to conclude this origin story of Adam’s work as a tiller of the ground.