Abram, called out of idolatry to follow the living God, is still growing in faith as we see him here. Even though he has great promises concerning the coming of Messiah from his line, he fears for his life when famine sends him down to Egypt. He commits a sin and causes his wife to sin also in deceiving Pharaoh. We see that the Lord judges Pharaoh, even though he was unaware of the relationship between Abram and Sarai. We also see that in spite of the sin that Abram committed, the Lord brought good out of it and prospered Abram.
We are challenged to trust the Lord and not allow the fear of man to drive us into sin. But we are also encouraged that even our lower spiritual states and our occasional lapses into sin will be used by the Lord for our ultimate good.