The seemingly strange account of Abram and Sarai faking out Pharaoh is a microcosm of the later Exodus account. Abram and the descendants of Israel initially were welcomed and exalted, but then they were seen as a curse and told to leave, sent away with many gifts and riches.
This is the second time Nathan had to come to David with a word from the Lord, at least the second time recorded in Scripture. But this time David spoke the prophetic word upon himself.
In Genesis 12 we hear God’s great command to Abram “go forth from your country” to establish God’s ambassadorial nation, Israel. We also see the great man of faith, Abram, needed to mature in his faith, as we do.