1. God deals with his people by covenanting with them. From the Garden of Eden on, God makes arrangements with his people that bind both parties. There are promised blessings for covenant faithfulness and promised curses for covenant unfaithfulness (Gen 2:15-17).
2. These covenants have implications for the recipients and for their children. Adam’s fall affected all his descendants (Rom 5:12-13). In the same way, God promised to be God to Abraham, and to his children after him (Gen 17:7).
3. God’s covenant with Abraham included a physical sign that was given to his children. The sign of circumcision was to be given to all Abraham’s male children—in fact, to every male in his household (Gen 17:9-14).
5. This New Covenant also has a physical sign that sets God’s people apart from the world. Baptism is now the mark that makes a distinction between the people of God and the world (Matt 28:19).
6. The signs of circumcision and baptism point to the same reality. Paul describes Abraham’s circumcision as a “seal of the righteousness he had by faith” (Rom 4:11). Baptism is also a sign of justification by faith (Rom 6:3-4). (“Righteousness” and “justification” translate the same Greek word.)
7. God makes a distinction between the children of believers and those of nonbelievers. In 1 Cor 7:14, Paul says that the children of at least one believing parent are “holy,” where they would otherwise be “unclean.” This is covenantal language, similar to what we see in the book of Leviticus: people, places and things are either “unclean,” common, or they are “holy,” set apart for God.
8. There is no indication in the NT that the covenant sign is no longer to be given to the children of believing parents. It would never have occurred to a first-century Jew, upon coming to Christ and embracing the New Covenant, that the covenant sign was not to be given to his children. For over a millennium God had promised to be God to his people and their children after them. If there was to be a change in the covenantal status of children, it would need to be explained to Jewish believers, and we see no such explanation.
Why do we baptize children? No one is saved by being born into a believing family. We are saved by the work of Christ, which we receive by faith. Infant baptism is based not on the assumption that these children are or will be saved, but on the fact that God regards the children of believing families as part of his covenant family. Our children are not of the world; they are of the church, God’s visible family on earth. As such, they have a right to the mark that sets God’s people apart from the world.