A friend recently asked me to explain what the sign of the new covenant is for Christians today. That can be a thorny 
question. A few years ago, another blogger sought to answer the question and hinted that it might be the Lord’s Supper. Most have supposed the sign of the new covenant to be baptism. Here is my attempt to answer.
Without a doubt, Jesus links the Lord’s Supper to the new covenant: “Drink from it, all of you; for this is My blood of the covenant, which is poured out for many for forgiveness of sins” (Matthew 26:28, NASB).
Paul, likewise, uses the same language in his repetition of the elements of the Lord’s Supper (1 Cor 11). Nevertheless, I believe the Lord’s Supper is prescribed as a sustenance ordinance; it signifies ongoing participation in the new covenant community. I don’t believe it is the primary sign of the new covenant because I don’t think it is the primary ordinance offered by Jesus. The primary sign of the new covenant appears to me to be believer’s baptism. Here is a brief argument in three steps which shows the significance of the sign of believer’s baptism.
Born Again
Much is made of circumcision in the Old Testament and its displacement in the New by baptism, but the issue is a little more complicated than simply a switching of the signs. The New Testament is not concerned with a mere changing of a team’s uniform from one outward appearance to another. The New Testament speaks of a new day in which all of creation is being renewed (1 John 2:8). This new day ushers in a new era in which the people of God have the law written by the Spirit on their hearts (Jeremiah 31:33).
The significance of this change is pointed out by Jesus in John 3 when he tells a leading teacher of the Jews that he must be born again. When this teacher (Nicodemus) acts confused, Jesus chides him for not understanding what the prophets spoke about (see Jeremiah 31; Ezekiel 36:25). The prophets were speaking of a pouring out of God’s Holy Spirit which would usher in a new era of God’s people. God’s people would be marked not by occupying the land of Israel or by having an earthly king like David; they wouldn’t necessarily be marked by circumcision. Rather, they would be marked by spirit-filled obedience, having been born again from above.
As a result, New Testament writers make much of the necessity first and foremost of being born again by the regenerating work of the Holy Spirit (Eph 2:5, 10; Rom 8:9; 1 Peter 1:3, etc). If anything, the sign of the covenant offered in the New Testament is the sign of those having the law of God written on their hearts. Being born again is the surest sign of being in the new covenant community.
Believer’s Baptism
Therefore, the one action that most closely signifies the work that God does in regenerating a human soul is the sign of believer’s baptism. Baptism itself is not enough to satisfy the expectation of the Old Testament prophets (f by baptism you mean merely an outward, covenant sign). The prophets were already protesting the false security of the Jews, who vainly claimed covenant status because they were “circumcised.” Like Paul after them, the prophets shouted, “The sign is not the point” (See Romans 2:28-9; 1 Cor 7:19; Galatians 6:15).
The New Testament does not demand baptism as a mere covenantal nicety. It demands baptism as an affirmation of regeneration. Baptism by immersion follows as an act of private and corporate obedience, affirming the work accomplished by God of washing a soul clean and raising it up as a new, indestructible life. As such, believer’s baptism signifies much more than community membership. The very essence of baptism is regeneration and resurrection. Membership in community is only significant in that the new member is one who has been born again of the Holy Spirit. (The reality is that regeneration must be present for baptism to be valid, which is why the solution to the problem in Acts 19:1-5 was to baptize these followers “again.”)
Signs Insufficient
The necessity of the work of the Holy Spirit preceding baptism is the point of the new covenant community. In Baptist circles, we call this necessity “Regenerate Church Membership.” Practically, however, it means that the church should hear professions of faith from candidates before walking with them into the waters of baptism. As with Philip at the end of Acts 8, the pattern is clear: Preach Jesus, baptize those who confess faith in Jesus (see also Acts 16:33-34, in which the household was baptized because they had believed).
The point of what I am saying is this: Do not put confidence in any sign—even in believer’s baptism. The significance of believer’s baptism as the sign of the New Testament Church is not the “Baptism” part of the sign, but the “believer” part. Baptism saves no one. Faith in Christ is all that counts for saving one’s soul. So, those saved by grace through faith will be baptized and will continue celebrating their faith in community through the Lord’s Supper observance.
Gregory C. Cochran 