Genesis 17:15-27
Same theophany, second petuchah. Gen 17:15-27 names what Gen 17:1-14 inscribed. Sarai becomes Sarah; Abraham laughs inwardly at the announcement and the child is named for the laugh; God says aval - truly - and the covenant narrows from Abraham's seed generally to one named son not yet conceived. Ishmael receives the creation-mandate blessing every nation can receive; Isaac receives the berit olam. At Mamre the angel will quote this annunciation back: shall a word be impossible with God? Luke quotes the angel back over Mary. The child's name is the disbelief converted into gift, and the seed-bearer is the woman God blesses by name.
Genesis 17:1-14
After thirteen years of silence following Ishmael, Yahweh appears to Abram at ninety-nine and names himself by a name the older Greek witness will quietly suppress. He commands the walk that Noah walked, gives the sign that the rainbow gave, and inscribes the covenant into flesh. Gen 17 is where the canon places its closed set of two: the bow in the cloud and the cut in the body — the only two covenant-signs Scripture designates with the precise formula ot berit. The article reports what the text says before tracing how heart-circumcision and the eighth day carry the chapter forward across six centuries to Paul.