It seemed fitting to follow up my post about Jesus on Circumcision with "Stephen on Circumcision." Except Stephen really doesn't say much about circumcision. I finished listening to the book of John and as to be expected the books of Acts started. I've decided to read through Acts again once I've finished the Bible because they are many small details I just don't remember. But this portions of Stephen's speech caught my attention today,

8 And he gave him the covenant of circumcision. And so Abraham became the father of Isaac, and circumcised him on the eighth day, and Isaac became the father of Jacob, and Jacob of the twelve patriarchs. - Acts 7:8 (ESV)

Now there isn't much here. But yet again I have a couple thoughts. Though this time I will move outside of Acts 7.

1. Circumcision is the Covenant. This is quite plain. This is found at the very founding of God's covenant with Abraham (Gen 17:1-14). The consequence of neglecting circumcision is to not be in the covenant (Gen 17:14). Even more interesting, a person can't participate in the Passover unless all his children are circumcised (Exo 12:48). Yes, circumcision is the sign of the covenant. But it is such a sign as to actually be the covenant itself.
2. Circumcision is a seal of Righteousness. This points builds off the last and moves into the teaching of Paul in Romans 4. There Paul says circumcision was to Abraham a "seal of the righteousness that he had by faith" (Rom 4:11). It is because of this that some argue that Abraham's circumcision was different than Isaac's. And I completely agree. For Abraham, it was the covenant received by faith for the purpose of making him "the father of all" (Rom 4:12). Abraham's "conversion circumcision" was necessarily unique [narrative not normative] for the purpose of showing the power of the gospel to Gentiles.
3. Circumcision is the Promise of Offspring. Here is where people miss the most obvious truth about circumcision. It proceeds the giving to Abraham of the child of promise. Yes, Abraham has Ishmael and he gets circumcised. But the promised seed (of Eve) needs a lineage and that comes through Isaac (Gen 17:15-21). Circumcision points forward to Isaac! Circumcision is, in fact, the promise that God would bring offspring to Abraham that would call upon the Lord and be blessed in an "everlasting covenant" (Gen 17:19). Stephen picks up on this. Abraham had "no child" (Acts 7:5) then he receives the covenant "and so Abraham became the father." That "and so" could be translated "in this manner" or "thus" but the point is the same circumcision was the guarantee and source of Abraham's parenthood.

It is with all this in mind that portions of the New Covenant make pretty serious sense. In Ezekiel 37 God promises Christ (37:24), an everlasting covenant (37:26), to be their God (37:27), and all this blessing upon "children and their children's children" (37:25). God's New Covenant promises point to Godly offspring. 

No passage of Scripture has tied together God's concern in His promises for children more than Isaiah 59:21. Here God is so bold to promise that His Spirit and very Word will not depart from our children.

21 “And as for me, this is my covenant with them,” says the Lord: “My Spirit that is upon you, and my words that I have put in your mouth, shall not depart out of your mouth, or out of the mouth of your offspring, or out of the mouth of your children's offspring,” says the Lord, “from this time forth and forevermore.” - Isaiah 59:21 (ESV)