What makes the story of Avraham (Abraham) and Sarah going to Egypt important enough to be included in the Genesis narrative? (Genesis 12:10-20)  

Ramban suggests that this is an example of the maxim that what occurred to our patriarchs and matriarchs will one day occur to the Jewish people.  Note that Avraham migrates to Egypt because of a famine.  There, his wife Sarah is taken hostage; God intervenes by smiting Pharaoh and his people--ultimately Pharaoh ushers Avraham and Sarah out of the country.  

This precisely mirrors what happens later on in Bereishit.  Jacob comes to Egypt with his family because of a famine.  In time, the Jews, like Sarah, are enslaved; God intervenes with plagues and Pharaoh, King of Egypt, insists that the Jews leave. (Ramban, Genesis 12:10)  

Another observation.  God's covenant with Avraham includes a promise of land and children.  Relative to both of these commitments, Avraham is tested.  Among all the lands, the one that is promised to Avraham, the land of Canaan, is stricken with famine. Later, God asks that the only child born of Avraham and Sarah, Yitzhak, be taken to Moriah to be slaughtered. (Rashi, Genesis 12:10, 22:12)   

These two chapters are strikingly similar.  In the Binding of Isaac story God steps in to save the child at the last moment.  The covenantal promise of family is secured.  Here too, in the Egypt narrative, God steps in, punishing Pharaoh.  Avraham returns to Canaan.  The covenantal promise of land is sustained.  

The upshot: Covenants do not guarantee that the road will be smooth. Sometimes, even after the covenant is proclaimed, there are set-backs.  The test of belief is whether one can maintain belief during periods of challenge as did Avraham.  This is a central message of the Avraham--Sarah story in Egypt.  

One last thought.  The importance of this chapter may be the beginning of the covenantal promise to Sarah.  Up to this point, only Avraham was promised children.  Was Sarah part of this commitment?  After all, in this section, Avraham asks Sarah to proclaim she is his sister.  Children are not born from sibling relationships.  In fact, in Egypt Avraham is given shefakhot (hand maids). (Genesis 12:16)  One of them is probably Hagar whom Avraham ultimately marries. (Genesis 16:1)  

In the end, however, the Torah declares that God smites Pharaoh, "concerning Sarah, Avraham's wife." (Genesis 12:17)  Here, for the first time God acts on behalf of the relationship between Sarah and Avraham. From Sarah and not from Hagar, would come the child who would be the second patriarch.  This commitment from God makes this section extraordinarily important in understanding the unfolding of the Jewish people. 

Shabbat Shalom,

Rabbi Avi Weiss