Parshat Lech Lecha chronicles Avram’s development and maturation into the role that God designates for him: to be the seed of a new people whose values are rooted in justice and righteousness. God tells Avram to “be a blessing,” a cryptic phrase for the nascent leader and for us. What does it mean to “be a blessing?” As the parshah unfolds, we can trace Avram’s development into this role. His growth shows us what it means to embody justice and righteousness; to be a blessing.
The parshah chronicles Avram’s actions out in the world and in his own tent, giving us a sense that justice is equally important in public and at home. A series of episodes shows us that when his actions aren’t guided by justice, he fails in both arenas.
While in Egypt as a public figure, Avram pretends that his attractive wife, Sarai, is his sister in an attempt to avoid harmful relations with his Egyptian hosts. Pharaoh takes her as a mistress and Avram gains wealth as a result. However, when Pharaoh discovers the truth, he berates Avram and banishes him and Sarai from his country. Ramban goes so far as to claim that Avram’s immorality in Egypt ultimately causes his descendants to be enslaved there.
Avram fails similarly in his personal life when righteousness and justice are absent. At the beginning of the parshah, he renders his wife powerless and voiceless, both in his ruse with Pharoah and when he leaves his land with her: the text says that he literally “takes” (yikach) her with him.  The power imbalance that this language implies is palpable. Sarai’s silence persists for four chapters of the parshah, as Avram acts upon her rather than with her in their childless, inequitable relationship.
There is a pivotal change in the parshah when we see Avram begin to embody righteousness and justice both internally and externally. Publicly, this is most clearly demonstrated through his courageous and righteous dealings with foreign kings in a time of war. In two completely selfless acts, Avram organizes troops to rescue his nephew Lot from captivity and returns stolen wealth to neighboring kings. King Malki-Tzedek offers to pay him a great reward for the military feat, yet Avram declines the gift.  His intent was to do justice, not to earn a profit—a stark contrast from his behavior in Egypt.
In the private sphere, Avram turns around his relationship with Sarai. She finally breaks her silence, and the text says that “Avram listened to the voice of Sarai.” Compared with the dominant position illustrated by the earlier passage, this new language connotes an equitable relationship (vayishma—he listened, rather than vayikach—he took). After this key change, in the very next chapter, God promises Avram that his wife will be blessed and that she will bear a son.
Avram’s public and personal maturation is poetically confirmed in the parshah’s conclusion. God adds the divine letter heh to his name, so that publicly he is to be known as Avraham for the rest of his life. He then undergoes a circumcision, altering the most private part of his body. This twofold transformation of public and private serves as a mirror image of his growth as a leader and a husband.
According to this read, Parshat Lech Lecha suggests that true leadership must be a combination of justice personally and politically. When we genuinely work to increase justice and righteousness in our own lives, we also cultivate these values externally; when we actively address global issues, we set the stage for developing just personal lives. All of these actions intertwined are what make Avraham, and us, a blessing.
 Bereshit 18:19
 Bereshit 12:2
 Bereshit 12:13
 Bereshit 12:18-19
 Ramban on Bereshit 12:10
 Bereshit Rabbah 40:4
 Bereshit 14
 Bereshit 14:21-24
 Bereshit 16:2
 Bereshit 17:16-19