Abram goes to Egypt because of a famine in Canaan; this prefigures the Israelites in Egypt. But even more, it illustrates the sojourn of a regenerate soul in this world of famine and desert because of its rejection of God’s revelation in natural and special revelation.
Abram is the father of those honest about dependence, but that is still a function of God’s Word and Spirit, not something of Abram’s own nature or doing – thus Abram is still human and still fails to trust God. Thus, Abram tells a half-truth about Sarai in order to protect himself. Here we see more foreshadowing as Pharaoh takes what is not his and is plagued accordingly.
Abram returns to the place he was between Bethel and Ai. God’s great material blessing of Abram and Lot is a source of strife between their herdsmen. Abram, as a type of Christ, intercedes to make peace, inviting Lot to choose where he would sojourn. Lot, like materialistic, selfish human nature, chooses what he assumes is best for himself (remember Cain’s choice of vocation?) but that will become big trouble. God re-confirms His promises to Abram and adds a physical element of confirmation—Abram’s descendants will be as the dust of the earth.