Like so much material in Genesis, the covenant God makes with Abraham is recounted twice in this parashah. The second telling of the story is by the source designated P, and repeats two themes from the two previous parshiyot, joining them in the person of Abraham.
God introduces the covenant this way (Gen. 17:1–2):
When Abram was ninety-nine years old, YHWH appeared to Abram, and said to him, “I am El Shaddai. Go before Me and be perfect, and I will set my covenant between Me and you, and I will increase your offspring trememdously.”
God then subsequently changes Abram’s name to Abraham, and Sarai’s to Sarah, and institutes circumcision as the physical sign of the covenant.
What strikes me here is that the word used here when God tells Abram to “go”, hit’halech, is the same word we saw last week that the Torah uses to describe Noach (6:9) and Enoch (5:24). Furthermore, the Torah also describes Noach as tamim, “perfect”, which is exactly what God tells Abram to be. Remember that grammatically this verb is reflexive, meaning something like “go yourself”, and last week we saw that this denotes a special kind of behavior in one’s life, living in ways that are honoring of the earth and the people within it and of the sacred relationship between humanity and the divine. Even the name of this week’s parashah, Lech l’cha, reflects this: it is taken from the injunction God gives Abram: “Go [lech] for yourself [l’cha] from your land…” (12:1).
God then blesses Abram by changing his name to Abraham, inserting the letter heh—part of the four-letter Divine Name yud-heh-vav-heh—into his name, and He does the same with Sarai, changing her name to Sarah. This is an external sign of an internal change: Abraham and Sarah are now different people, marked not just internally by the covenant but externally by their names, as symbols of walking with God.
Much is made about how God changes Abram’s and Sarai’s names and then later will change Jacob’s name to Israel (32:29), but it’s interesting to note that here, God’s name also changes. Here, He identifies Himself as El Shaddai, midrashically understood to mean something like “God who is sufficient” (she- is understood to be short for asher, “who” or “that”, plus dai, “enough” or “sufficient”), but its actual meaning and origin have been obscured through history. It is a conceit of the P Genesis story that God does not identity Himself as “Yahweh” to anyone before Moses; here another name is used. As the covenant is spelled out and continues to evolve, God is undergoing a transformation of His own; this is reflected through the different names the character of Yahweh uses throughout the Torah, just as with the different names that the human characters bear.
And this goes back to what I said when discussing B’reishit: names are power, and creation of names is a powerful act. In Genesis 2, Adam gives names to the animals and names his wife, as the first act of power that he exerts over the other things in his world. God names things into existence in Genesis 1. The act of creation is divine, but when it is emulated by humanity through our speech acts, our acts of naming, we are “walking ourselves” with God.