In this passage, God confirms the covenant He has already made with Abram, reiterating the promise of many descendants, and the land that will be their inheritance. Previously Sarai had not been mentioned in the promises, but now God makes it clear that she also will be the mother of nations.
They also receive new names, Abraham and Sarah. These new names are not so very different from the old ones, but these new names signify their new identities as covenant people. Although not included in this reading, the intervening verses describe the sign of the covenant, circumcision, which is both the obedient response of covenant people and a reminder of belonging to God and the promises He has made.
Those familiar with this psalm for its opening line, which Jesus quoted as he hung on the cross and felt abandoned by God, may be surprised at the different mood of these later verses. Now the psalmist is confident of having been heard by God and of receiving blessings from God. He praises God and calls upon all the people of Israel to join in praise to God. Not only Israel but all nations of the world, he says, shall turn to God and worship Him.
While the earlier verses and their description of great suffering is not part of this reading, it is important to remember that context. We praise God, knowing what He has delivered us from, and we are able to go through times of suffering knowing that God has not forsaken us, even though it may seem so at the time.
Many Jews in the first century considered their physical descent from Abraham to be not only a source of great pride but the assurance of their being in a right relationship with God. Like Abraham, they were marked by the sign of circumcision, and they faithfully kept the Mosaic law – which some rabbis taught that Abraham had done also, having had it somehow revealed to him centuries before it was given to Moses.
Paul emphasizes that neither circumcision nor keeping the law were what put Abraham in a right relationship with God. He had believed God and his faith was “reckoned as righteousness” years before he was circumcised. And there is nothing in Scripture to indicate that he had any knowledge of Mosaic law. The blessings he received were based on his faith in God’s promises, and as such he is an example for us and our faith.
In the verses right before this passage, Peter has said that Jesus is the Christ, the Messiah. Jesus’ response surprised the disciples, who expected the Messiah to put an end to Roman oppression and usher in an era of prosperity and blessing. It might also surprise people today who think of faith in Christ as a way of finding solutions to their problems and securing God’s blessings.
Jesus not only tells the disciples not to go around telling anyone He is the Christ (which everyone else will interpret the same wrong way they have), he tells them that he is going to be rejected and killed (and then that he will rise again but they were probably too stunned by the thought of him being killed to really notice what he said next).
Peter is so sure of his own interpretation that he rebukes Jesus for contradicting it, at which point Jesus rebukes Peter in very harsh language. Not only does he need to die, but the disciples also and anyone else who would follow Jesus must also be willing to die. We think of this metaphorically, but for first century Christians it was a very real possibility, as it still is in many parts of the world.