I know, that is an ambitious title. These things are connected in our theology; or at least they should be.
When I interact with those who advocate for believers’ baptism they often point to the New Covenant which is said to be very different than the Old Covenant (it is in some significant ways). The New Covenant, they say, leads them to hold to a regenerate or pure church such that the difference between the visible and invisible churches to be nearly insignificant. While there is nothing in any of the direct statements about the New Covenant that prohibit infant baptism or demand believers baptism they think it does. They are using a good and necessary consequence argument to defend believers’ baptism. We Reformed paedobaptists also use an argument based on good and necessary consequence. The difference is that we acknowledge this but they usually don’t.
The author of Hebrews refers to the promise of the New Covenant twice: in chapters 8 and 10.
8 For he finds fault with them when he says:
“Behold, the days are coming, declares the Lord,
when I will establish a new covenant with the house of Israel
and with the house of Judah,
9 not like the covenant that I made with their fathers
on the day when I took them by the hand to bring them out of the land of Egypt.
For they did not continue in my covenant,
and so I showed no concern for them, declares the Lord.
10 For this is the covenant that I will make with the house of Israel
after those days, declares the Lord:
I will put my laws into their minds,
and write them on their hearts,
and I will be their God,
and they shall be my people.
11 And they shall not teach, each one his neighbor
and each one his brother, saying, ‘Know the Lord,’
for they shall all know me,
from the least of them to the greatest.
12 For I will be merciful toward their iniquities,
and I will remember their sins no more.” Hebrews 8
The author wants them to know that 1) the New Covenant is better and 2) the Old Covenant is obsolete. This does not mean the covenants are completely different and disconnected. The word used here for “new” is “kainos” instead of “neos”. “Kainos” can mean renewed rather than absolutely new. It can also refer to “more recent”.
One point of continuity between the 2 covenants is the subjects. God is a party in both covenants. So is “the house of Israel and the house of Judah.” This rules out dispensationalism, in my mind at least. There is not one covenant for Israel and one for the Church. This covenant is for Israel and Gentiles are brought into the true Israel (see Romans 9-11 among other places).
Another point of continuity is God’s law. This must be handled carefully. In Hebrews 10, he uses this same text to indicate that Christ fulfilled the sacrificial (ceremonial) law such that no sacrifices for sin are necessary. The temple, therefore, is obsolete and would soon be destroyed as a result (8:13). What law, then, is God talking about through Jeremiah? It isn’t a new law, but the same moral law.
The point of discontinuity is that the law will be written on their hearts, not on stone. Ezekiel adds that the Spirit will move us to obey the law. Another point of discontinuity is that the Spirit now dwells in those united to Christ.
Now… where does this text teach that all in the covenant community are regenerate? Where does this text teach or indicate that only those we think are regenerate are to be baptized?
What we do find in the surrounding context in Hebrews is a series of stark warnings against turning away from Christ and returning to the Old Covenant. It was possible, therefore, for those in the covenant community, including those who professed faith to turn away from Christ. Apostasy was a real possibility precisely because the church was not pure, but mixed. In this way it is just like Israel in the Old Testament.
Another point of continuity is with the covenant with Abraham seen in the “I will be there God.” This was a central feature to the promises given to Abraham in Genesis 15 and 17. There the promises were to “you and your children.” Peter uses this same language in his Acts 2 sermon. Paul indicates that we are saved thru God’s covenant with Abraham in Galatians 3.
These factors lead me to think that since the covenant with Abraham included children who received the sign of the covenant, this New Covenant should also contain the children who receive the sign of the covenant. The elements of the New Covenant don’t point me away from infant baptism, but toward infant baptism.
Back to the reality of apostasy. Let’s see a few passages:
4 For it is impossible, in the case of those who have once been enlightened, who have tasted the heavenly gift, and have shared in the Holy Spirit, 5 and have tasted the goodness of the word of God and the powers of the age to come, 6 and then have fallen away, to restore them again to repentance, since they are crucifying once again the Son of God to their own harm and holding him up to contempt. Hebrews 6
26 For if we go on sinning deliberately after receiving the knowledge of the truth, there no longer remains a sacrifice for sins, 27 but a fearful expectation of judgment, and a fury of fire that will consume the adversaries. Hebrews 10
There are two main ways we can understand this. One is to deny the doctrine of election which consistently taught in the Scriptures. I guess you could make it a conditional sort of election; you are in unless you commit apostasy. The other is to understand that “not all Israel is Israel” (Romans 9). Those in the covenant community include people like Isaac and Ishmael, like Jacob and Esau. In both cases the brothers were circumcised. One would receive the promise by faith and the other would not. Remember, this is under the Abrahamic covenant by which we were saved. Circumcision did not mean they were saved. It was a sign that “righteousness was received by faith” (Rom. 4). This is the same thing baptism says!
I think we need to understand these warnings in Hebrews in light of Deuteronomy 29.
18 Beware lest there be among you a man or woman or clan or tribe whose heart is turning away today from the Lord our God to go and serve the gods of those nations. Beware lest there be among you a root bearing poisonous and bitter fruit, 19 one who, when he hears the words of this sworn covenant, blesses himself in his heart, saying, ‘I shall be safe, though I walk in the stubbornness of my heart.’ This will lead to the sweeping away of moist and dry alike. 20 The Lord will not be willing to forgive him, but rather the anger of the Lord and his jealousy will smoke against that man, and the curses written in this book will settle upon him, and the Lord will blot out his name from under heaven.
The context is the same, a person is turning away from the Lord to serve false gods. In Hebrews they are turning away from Jesus, the Lord, to return to an obsolete covenant that points to Christ but denies Christ’s work by continuing to offer sacrifices. They are the ones God will not forgive, because they’ve rejected the sacrifice of Christ.
Under both the New and the Old Covenants, there are people who were in the covenant community who turn away from the living God. They return to the gods of the nations or the prior administration. In either case they turn away from the God who redeemed them. In either case we do not find a “pure” or “regenerate” church. We find that credobaptists are building their house on sand, a faulty understanding of the covenant.