Today we read about circumcision and its importance, in John 7 and 4 chapters in Genesis. But that is just one part of the story.
John 7:1-24. Jesus pointed out that according to Jewish law, circumcision is more important than keeping Sabbath, so, if the eighth day is on a Sabbath, it must be performed, but healing on a Sabbath is not permitted.
In Genesis15 God promised Abram a son, and Abram believed God and it was counted to him as righteousness.
But in Genesis 16 Abram badly wanted an heir, so Sarai, being too old, gave her handmaiden Hagar to be mother of Abram’s son, Ishmael. Sarai regrets what she had done, and Hagar was sent away with Ishmael into the wilderness.
Thirteen years later, in Genesis 17, Ishmael was back with Abram, God promised Abram his seed of promise, changed Abram’s name to Abraham and Sarai’s name became Sarah, established with an eternal covenant, the covenant of Circumcision, and it was performed on Abraham, Ishmael and all Abraham’s male servants.
Which brings us to Genesis 18 with Abraham still waiting for his promised offspring. He was visited by three angels that promised him he will have a son within a year. Sarah heard it and found it laughable, but God confirmed this promise, and was also proclaiming the destruction of Sodom and Gomorrah. Abraham tried to bargain with God at no avail.
The question to ponder: Why is circumcision important for Jews and Muslims, but not for Christians? Hint: read the Acts of the Apostles, chapter 15.