Names switch three times in this passage: the familiar Abram to Abraham; the less often remembered (but more impressive) Sari to Sarah; and the seldom noted YHWH to El Shaddai. The name changes in this passage seem to coincide with what is going on with the character.
Abram to Abraham is actually the least interesting change. To most ears at the time, it would have been the same name, simply spelled a bit differently. The meaning of each seems to do with a father or ancestor (the Hebrew Ab – like the New Testament’s Aramaic Abba). The switch in spelling, at first anyway, appears to be akin to switching Charlene to Sharlene or Matt to Mat. No big deal.
But there is a word play going on. At other times when God promised Abram many descendants, God doesn’t change the name. Abram already means something like “Exalted Father.” The promise is already in his name. For example, in Genesis 15, God shows Abram the stars and says your descendants will number as many – with no name change. But in chapter 17, God uses the word “multitude” or “crowd” to describe the number of Abram’s descendants. In Hebrew, that word is Hamon. So Abram’s name is changed to contain the word ham (multitude), and we get Abraham: Father of multitudes. Abraham’s new name simply matches the way God is talking about the covenant in this context.
Abraham’s new name is interesting if one takes the time to look for it. But it is otherwise no big deal. “Father Abraham had many sons, and many sons had father Abraham.” The song means the same thing if you say Abram.
Sari’s name change is immediately more significant. The name Sari itself doesn’t mean much of anything. It is just a name, the way most people in the US just have a name (very few people make note that Matthew means “gift of God” – it is just a name to me and most other Matthews out there). Sari was a name like that. But Sarah – that word means “queen” or “princess.” Sara’s new name gives her a royal title: the queen mother. This change strikes so powerfully that neither the writer nor God have to point it out (though they do note, as they did with Abraham, that kings will descend from her). God’s covenant with her changes her very identity.
God has two names in this story, too. The narrator calls this God YHWH, “the Lord.” That is, of course, the name God reveals to Moses at a much later time. The narrator wants us to know that this encounter between God, Sarah, and Abraham is the same God, the one true God. But God’s own self-revealed name to the couple is El Shaddai (the NRSV attempts to translate this for us as “the Almighty”). The most interesting theory on El Shaddai I have come across, is that, in Genesis, this name is used of God when God is granting fertility. It is God’s “fertility goddess” name. This may be one of the times God uses a feminine image of herself.
How might one preach this passage?
One could connect this passage with the second reading today, from Romans, about faith. If you were to do that, I’d read a bit farther in the Genesis story, through verse 19. You might look at Abraham’s response: to fall down in worship and to laugh (which becomes the name of Sarah’s son). You might consider how laughter can be a way to show faith – perhaps joy at God’s outrageous promise?
When God says to us: “Look, I’m making all things new!” and promises to “Wipe away every tear from their eyes. Death will be no more. There will be no mourning, crying, or pain anymore, for the former things have passed away.” When the resurrection of Jesus is proclaimed and our inclusion in the people of God is announced, perhaps we need to simply fall on our face and laugh.
Another preaching tactic might be to focus on the name changes. God speaks reality into our lives. God names us. The names God has for us are good names that give us much hope. If you go this route, you’ll have to pull in some other scriptures that name us. Perhaps God’s name for Jesus at the baptism, which becomes our name when we are baptized, would be a good one to include: “You are my child, whom I love, in you I find happiness.” Perhaps our name, “Royal priesthood.” And there are others – have fun with it!
Finally (for me – there are dozens of ways to preach this), a preacher might focus on what God asks of Abraham: “walk with me and be trustworthy.” The words “walk with me” or “walk before me” are a way of expressing an ongoing journey in full view of God. Being watched by God, as we journey before God, can encourage us (God is with us!) and it can and challenging us to walk worthily. The other command (and they are both commands) is to “be blameless” (NRSV) or “be trustworthy” (CEB). I think the CEB captures the meaning better here – it is a positive quality, not a negative one, that can also mean “whole” or “sound.” Be a person of integrity, be trustworthy. God’s covenant and promises are fully on God – they are gifts. But God does want us to play along and these two commands are a good summary of what God wants from us: “Walk with me and be trustworthy.”
May we all walk before God and be trustworthy! [PS – the lectionary never has us read Genesis 17:9-14. These verses, however, are important. They speak of the everlasting and permanent nature of the practice of male circumcision for God’s people. The severity and explicit nature of this passage makes what happens in the New Testament all the more striking. God gives the Sprit to uncircumcised gentiles. WHAT!?! These people are breaking the Bible’s clear teaching! They are not circumcised, they eat the wrong foods, and they don’t keep Sabbath! And yet, here is God, including them. The enormous shift that the church makes regarding circumcision (and food laws and Sabbath laws) cannot be overstated and the implications may be with us even still. So, you might want to hold on to Genesis 17:9-14 to read along with portions of Acts 10 on the Sixth Sunday of Easter. You could also read these today and, again, apply them to the Romans passage that addresses faith being the marker of the people of God, not anything else.]
 See, for example, http://www.jrdkirk.com/2012/02/02/imaging-the-biblical-god . I once preached a sermon where I looked at many of the feminine images of God. One main point in that sermon was to say that God is not a man. I had several people leave my church after that sermon. Proceed with caution!
 Rev. 21