Daily, mysteriously, the Holy Spirit uses the ministry of the Word and the prayers of believing parents to bring baptized covenant children to new life and true faith. More than a few covenant children never remember coming to faith because they have always believed.
Jackson writes to ask, “As it relates to continuity with the Abrahamic covenant, for example, Abraham and his children get circumcised, therfore in the new administration, Jesus and his children (spiritual) get baptized. Do you think that someone can retain their Reformed confession of the WSC and still be Baptist if they use that kind of reasoning?”
The essence of the question is the nature of the continuity of between the new administration of the covenant of grace and the Abrahamic administration of the covenant of grace. Under Abraham the promise was to believers and to their children and it included the external administration of the sign of the covenant to believers and to their children. Genesis 17:1–14 says:
When Abram was ninety-nine years old the LORD appeared to Abram and said to him, “I am God Almighty; walk before me, and be blameless, that I may make my covenant between me and you, and may multiply you greatly.” Then Abram fell on his face. And God said to him, “Behold, my covenant is with you, and you shall be the father of a multitude of nations. No longer shall your name be called Abram, but your name shall be Abraham, for I have made you the father of a multitude of nations. I will make you exceedingly fruitful, and I will make you into nations, and kings shall come from you. And I will establish my covenant between me and you and your offspring after you throughout their generations for an everlasting covenant, to be God to you and to your offspring after you. And I will give to you and to your offspring after you the land of your sojournings, all the land of Canaan, for an everlasting possession, and I will be their God.”
And God said to Abraham, “As for you, you shall keep my covenant, you and your offspring after you throughout their generations. This is my covenant, which you shall keep, between me and you and your offspring after you: Every male among you shall be circumcised. You shall be circumcised in the flesh of your foreskins, and it shall be a sign of the covenant between me and you. He who is eight days old among you shall be circumcised. Every male throughout your generations, whether born in your house or bought with your money from any foreigner who is not of your offspring, both he who is born in your house and he who is bought with your money, shall surely be circumcised. So shall my covenant be in your flesh an everlasting covenant. Any uncircumcised male who is not circumcised in the flesh of his foreskin shall be cut off from his people; he has broken my covenant” (ESV).
There are two aspects to the promise as it was articulated in Genesis 17: children and the gentile nations. In connection with this expression of the promise (see also Gen ch. 12 and 15) Yahweh changes Abram’s name to Abraham. He will be the father of a multitude of nations. In v. 9 Yahweh articulates the second aspect of the promise, to be Abraham’s God and a God to his children.
Yahweh gave a sign and seal of the promise: circumcision. It was a bloody, typological sign pointing forward to the death of Christ (Col 2:11–12) and he commanded that the sign be applied both to Abraham the believer (Gen 15:6) and to his sons. The external administration of the covenant of grace under Abraham included both believers and children. This is significant for New Covenant believers because Paul invokes the Abraham promise as the pattern for the New Covenant:
For the promise to Abraham and his offspring that he would be heir of the world did not come through the law but through the righteousness of faith. For if it is the adherents of the law who are to be the heirs, faith is null and the promise is void. For the law brings wrath, but where there is no law there is no transgression.
That is why it depends on faith, in order that the promise may rest on grace and be guaranteed to all his offspring—not only to the adherent of the law but also to the one who shares the faith of Abraham, who is the father of us all, as it is written, “I have made you the father of many nations”—in the presence of the God in whom he believed, who gives life to the dead and calls into existence the things that do not exist (Rom 4:13–17; ESV).
Abraham is the father of all Christians, both Jew and Gentile. Abraham believed before he was circumcised, when he was a Gentile and thus he is the father of all Gentile Christians, and he believed when he was circumcised and thus is the father of all Jewish Christians.