God called his people to be distinct ("set apart, holy") from other nations. That way, the other nations could see this blessed nation and be drawn to meet the one, true, loving God (Genesis 12:1-3).

Since the time of Abraham, God's people were set apart by circumcision (of males, and usually as babies—Genesis 17:9-14). But that eventually led to a major question in the early church, as the Lord sent his renewed people, who were mainly Jewish, to bring the gospel to Gentiles and welcome them into his family. Did Gentiles have to be circumcised in order to be fully Christian? The early church eventually concluded, "No." Since God was already accepting them through the Holy Spirit, they needed to be received into the church through baptism. Baptism, not circumcision, became the primary way that all of God's people (Jews and Gentiles) were set apart as holy.

So in the church today, adults and children, including infants, are set apart as "holy" in baptism just as adults and children in Israel were set apart by circumcision. Throughout the centuries, the church has practiced baptism this way as the sign of God's lasting covenant with his people, welcoming all who are in the households of believers into the family of God.