FRANCIS A. SCHAEFFER: BAPTISM (Infant Baptism - Unity of the Covenant)

We do not believe that those who are Baptistic have any more Biblical grounds for teaching adult baptism only than they have for teaching immersion only.

As we begin our thinking on this subject, let us place ourselves in the position of a Jew who has been saved in the early Christian era. He is a Jew, and now he has put his faith in the Lord Jesus Christ. His mind has not changed overnight, and certain great truths which his people have known and believed for two thousand years are much in his thinking.

Salvation by Faith Alone
First of all, a Jew saved in the early Christian era would realize that even as he had been justified by faith alone, so also Abraham had been justified by faith alone two thousand years before. Romans 4:1-a makes this abundantly clear: "What shall we say then that Abraham our father, as pertaining to the flesh, hath found? For if Abraham were justified by works, he hath whereof to glory'; but not before God. For what saith the scriptures? Abraham believed God and it was counted unto him for righteousness." Galatians 3-6 is just as definite: "Even as Abraham believed God, and it was accounted to him for righteousness."

The fact is that the Bible carefully emphasizes that Abraham was justified by faith and that only, just as we are. It is a serious mistake to believe that anyone in any dispensation, has been or can be saved in any other manner than by faith plus nothing. Religious or moral obedience has no place as far as personal salvation is concerned in any dispensation. Notice that it is Paul's writings that stress this fact so clearly.

The Covenant Is Immutable or-the Unity Of the Covenant
Secondly, the Jew saved in the early Christian days would realize that the Covenant made with Abraham is Immutable, that is, unchangeable. Hebrews 6:13-18: "For when God made promise to Abraham, because he could sware by no greater, he sware by himself. Saying, surely blessing I will bless thee, and multiplying I will multiply thee. And so, after he had patiently endured, he obtained the promise. For men verily sware by the greater: and an oath for confirmation is to them an end of all strife. Wherein God, willing more abundantly to show unto the heirs of promise the immutability of his counsel, confirmed it by an oath: That by two immutable things, in which it was impossible for God to lie, we might have a strong consolation, who have fled for refuge to lay hold upon the hope set before us."

This passage is very' definite that, first, the Covenant made with Abraham is unchangeable, and that, second, it includes us who are saved in this dispensation.

Covenant Is Primarily Spiritual
This Jew would also remember that the Covenant made with Abraham was primarily spiritual. For those of us who are Gentiles saved in this era the national promises made to the Jews do not apply, but the spiritual promises do apply. Romans 4:16 is clear concerning this. The 13th verse tells us definitely that God is here speaking of the promise to Abraham, and yet verse 16 is equally clear that we, the Gentiles saved in this present era, are the fulfillment of that promise. "Therefore, it is of faith, that it might be by grace; to the end the promise might be sure to all the seed; not to that only which is of the law, but to that also which is of the faith of Abraham; who is the father of us all." Therefore, the promise could not be primarily national, but spiritual. Galatians 3:7,8,13,14 and 25 tell us exactly this same thing. We, the Gentile Christians, are the fulfillment of the promise made to Abraham; therefore, (though there is a natural, national portion of the Abrahamic covenant) the promise is not primarily national but spiritual. These passages also show that there is a spiritual unity in all dispensations.

Galatians 3:17 makes it abundantly plain that the spiritual promise made to Abraham was not set aside by the giving of the Mosaic Law four- hundred and thirty years afterward. The spiritual unity was not broken by the giving of the law on Sinai.

This Jew of ours, therefore, would have in his mind that Abraham was saved in the same manner as we are saved; and that the promise made to Abraham is Immutable and primarily spiritual; and further, that we who are saved in this dispensation are included in that promise. He would have in mind the Unity of the Covenant.

Source: https://www.fivesolas.com/fs_bapt.htm