Genesis Genesis 21:1–34
Genesis 21 opens with the verb that will become the canon's word for divine intervention and closes with the divine epithet that will become the canon's word for God's eternity. Between them the narrator stages a birth, an expulsion, a wilderness rescue, a seven-fold oath, and a tamarisk planted at a well. Sarah speaks the Edenic expulsion-verb in the imperative; Yahweh ratifies her. God opens Hagar's eyes the way Eden's were opened, but to a well of water this time. The chapter is built as the Akedah's dress rehearsal, and two of its verses become the most exact verbatim citations of Genesis in the New Testament.
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.