The new covenant is the new administration of the Abrahamic covenant. Just as the typological (looking forward) sign and seal of admission to the administration of the covenant of grace was applied to Abraham’s children (beginning with Ishmael) so the sign and seal of admission to the administration of the covenant of grace is applied to the children of believers (Acts 2:39; 16:15). In response to the Abrahamic paradigm frequently comes the objection: “But Galatians 3:16 says the promise is to “the seed” not to ‘the seeds.’ Does that not tell us that the Abrahamic pattern has effectively ended and been replaced by the Baptist approach of believer-baptism?”
It is true that Galatians 3:16 says that the promise is, to quote Paul, “to his seed.” It is quite true that, as Paul says, the word seed is in the singular. That truth, however, cannot work against the inclusion of covenant children in the administration of the covenant of grace. We know this from Genesis 17. It follows the same pattern in Genesis 12:7, 13:15; 15:18; and 17:7. Scripture says,
And I will establish my covenant between me and you and your seed after you throughout the generations for an everlasting covenant, to be God to you and to your seed after you.
Does the fact that God made a promise to the seed in the singular mean that covenant children are not involved in the administration of that promise (the new administration of the covenant of grace)? Of course not. We cannot assume the Baptist premise that the substance (that which makes a thing what it is) and the administration (the sphere where and the means by which the promise is received) of the covenant of grace are identical. They are not. In the very same place where scripture uses the singular, which Paul interprets to refer principally to Christ, believers are commanded to apply to their children the sign and seal of initiation into the administration of the covenant of grace.
One reason evangelicals sometimes have difficulty with this is the conflation or confusion of two categories: substance and administration. In the Baptist approach, only those who are believed to have already received the substance of the covenant of grace, i.e., Christ and his promises, by grace alone, through faith alone are allowed to receive the sign and seal of entrance the covenant of grace. In effect, the sign of initiation becomes a sign of renewal or recognition of what has already taken place. In the Abrahamic paradigm, however, initiation and recognition of reception are not the same thing. That’s why there are two sacraments: baptism (initiation) and the Lord’s Supper (recognition or renewal). Following the Abrahamic pattern, we initiate the children of believers on the basis of the divine command (Genesis 17; Matthew 28:18–20) and we pray with and for them, we catechize them, we nurture them in the family and congregation through the due use of ordinary means (Westminster Shorter Catechism 88) and when, by God’s grace, they give evidence of spiritual life and make a credible profession of faith, they are admitted to the Lord’s Table, which is the sign and seal of recognition of what has taken place. In the Abrahamic pattern, the administration of the covenant of grace is one thing and the substance of the covenant of grace is another. We administer the sign and seal of admission on the basis of divine command and promise, not on the basis of what we think to have occurred in a particular person.
This is how it worked in Genesis 17. It is certainly true that the substance, that is the promise (Christ and his salvation), was received only by grace alone through faith alone in Christ alone (who is the promised seed) but that promise must also be administered. It is not possible, ordinarily, to have to the things promised in the absence of administration. Paul says in Romans 10.
How then will they call on him in whom they have not believed? And how are they to believe in him of whom they have never heard? And how are they to hear without someone preaching? 15 And how are they to preach unless they are sent? As it is written, “How beautiful are the feet of those who preach the good news!” 16 But they have not all obeyed the gospel. For Isaiah says, “Lord, who has believed what he has heard from us?”
That same principle was true in Genesis 17 where “seed” is in the singular and refers to Christ. Nevertheless, children were still commanded to receive the sign and seal of the covenant of grace. It will not do to set Galatians 3 against Genesis 17.
We can confirm this interpretation by looking at the rest of Galatians 3. In verse 19 it confirms the interpretation that seed/offspring is singular. It will help to recall the problem that Paul is addressing in Galatians: the relation between the old/Mosaic covenant to the Abrahamic covenant. His argument is that the Abrahamic covenant is permanent and the Mosaic covenant is temporary. The Judaizers had reversed that order. They were seeking to make the Mosaic covenant fundamental and the Abrahamic the addendum. That’s exactly backwards. Thus, it is perverse to use Paul’s argument for the permanence of the Abrahamic covenant as a way of excluding children from the administration of the Abrahamic covenant—as if the Abrahamic covenant was just as temporary as the Mosaic. According to Paul it is not. The Abrahamic covenant is fundamental and permanent. The Mosaic covenant was temporary. That is why the old, Mosaic covenant is said to be fading, temporary, and inferior in the NT (2 Cor 3; Heb 7–10) but such things are never said of the Abrahamic covenant. No, he is the father of all who believe (Romans 4; Galatians 3–4).
Nevertheless, as Paul interprets Genesis 12, 15, and 17 we know that it does not exclude the reality of the administration of the covenant of grace or the inclusion of the children of believers in that administration, or even the truth that in Christ we are all seeds because he says so later on in the same chapter. He says,
For as many of you as were baptized into Christ have put on Christ. There is neither Jew nor Greek, there is neither slave nor free, there is no male and female, for you are all one in Christ Jesus. And if you are Christ’s, then you are Abrahams offspring, heirs according to the promise (Galatians 3:27–29; ESV).
Do you see here how Paul relates the singular “seed” to the plural “seeds”? We do not have to choose between them. Both are true. Christ is the seed but all those who are in Christ are now seeds. That was true under Abraham (John 8:56; Hebrews 11) and it is true in the new administration of the covenant of grace.
It is appropriate to speak of the administration of the covenant of grace relative to the seed and seeds. Paul does this in this passage. He’s talking to the Galatian congregation about their status in Christ and he uses baptism as a way of explaining that. We know that Paul is not saying to the Galatians that they are seeds by virtue of their baptism. That is the very error that he was combating. No, he is saying that baptism illustrates what is true of the believer.
This passage is best understood on the Abrahamic paradigm (in contrast to the Baptist paradigm) because it is following the Abrahamic paradigm from Genesis. In other words, Paul was not a Baptist. He didn’t make Baptist assumptions about the nature of the new covenant and about the Abrahamic covenant. He was a Paedoaptist just as he had been a paedocircumcisionist, If you will.
In short, all of the objections our Baptist friends offer could also have been made against the inclusion of covenant children in the administration of the covenant of grace under Abraham. Nevertheless, God still saw fit to include children in the administration of the covenant of grace under Abraham. Thus, the real issue here is the nature of the new covenant. That is why I keep saying that the new covenant is a new administration of the Abraham a covenant.
We do not have to choose between “the seed” and “seeds.” Christ is the seed but we become seeds by grace alone, through faith alone, in Christ alone and that happens ordinarily through the administration of the covenant of grace in the new covenant just as in the Abrahamic covenant, of which the new covenant is a species.