Just before He ascended to heaven, Jesus charged His followers: “All authority in heaven and on earth has been given to me. Go, therefore, and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all I have commanded you” (Mt 28:18-20). Jesus’ words make clear baptism is only for those who are following Him. As such, it’s a boundary line that marks them off from the world and identifies them as Christians.
Several other texts demonstrate that baptism is a visible, physical representation of various aspects of Christian conversion. Romans 6:3-5 explains that baptism is a reenactment of our spiritual death, burial and resurrection to new life in Jesus. 1 Corinthians 12:13 indicates it represents the Holy Spirit’s work of “baptizing” us into the body of Christ. 1 Peter 3:21-22 teaches it’s a symbol of rescue from judgment, picturing the washing away of our sins and the cleansing of our conscience. Colossians 2:11-14 tells us baptism is the New Testament fulfillment of circumcision, picturing the cutting away of our old, dead heart and replacing it with a new, living one. These texts combine to demonstrate that this ordinance has no meaning for people who have not trusted Christ for themselves.
Some traditions—which our church disagrees with but respects greatly!—teach that baptism is the exact New Testament counterpart to circumcision in the Old Testament. In this view, Christians should baptize their newborn infants, since circumcision was practiced on infants in the Old Testament. Circumcision was the sign of the Abrahamic Covenant, and it was expected that all males born into that covenant would receive the covenant sign. Likewise, baptism is the sign of the New Covenant; and, in this view, it is expected that all newborn children—male and female—should receive this covenant sign.
I (Josh) agree with all of this, right up to the point where we define “newborn children.” According to Jesus, the only way to enter God’s kingdom is to be “born again” (Jn 3:3). Thus, newborn children should be defined spiritually, not physically. Under the Old Covenant, physical birth was the defining factor; but under the New Covenant, spiritual birth is. Circumcision signified one’s connection with Abraham by blood; but in the New Covenant, baptism signifies one’s connection with Jesus by faith. In the Old Testament, a person entered God’s people by being physically born to a Jewish family; but in the New Testament, a person enters God’s people by being spiritually reborn into Jesus’ family.