The English word "baptism" comes from the Greek verb that means "to dip in water." In the Jewish Scriptures (Old Testament) there were laws that required priests to wash themselves before they could offer sacrifices to God (Exod 40.12-15). The high priest had to bathe himself before and after he went into the most holy place inside the sacred tent or the temple to make the sacrifice on the Day of Atonement (Lev 16.4, 23-24).

The prophets of Israel instructed the people to bathe themselves as a way of showing that they wanted to be pure and to do what God wanted them to do (Isa 1.16,17). At the site of the religious community in Qumran, archaeologists discovered a pool with a set of steps that the members used to walk down to the water and back up. These steps made it possible for members to wash themselves as a way of showing that they wanted their lives to be pure. During the same period in Israel's history, John the Baptist began preaching in the Jordan Valley. John told people to be baptized as a way of preparing themselves for the coming of someone who would be more powerful than he was, and who would bring the Holy Spirit to God's people (Luke 3.15-17).

Jesus may not have actually baptized anyone during his earthly ministry (see John 4.1,2), but he did tell people he had healed to undergo the ritual cleansing required by the Law of Moses (John 9.6,7). And later, before Jesus was taken up to heaven, he told his disciples to teach and to baptize people of all nations (Matt 28.18-20). His disciples obeyed his command, and Acts is full of accounts of how Jesus' disciples baptized new members, making them part of the Christian church. These new members were baptized to show that they wanted to stop sinning, turn away from their old way of life, and show that they were ready to enter a new life of obedience to God (Rom 6.1-4).

Acts begins with the story of how the Holy Spirit was sent to the church on the Day of Pentecost and how 3,000 new members were baptized (Acts 2.41). As the Good News of Jesus spread throughout Judea and across Asia Minor, new members were baptized, including many who were not Jews: Samaritans (Acts 8.12), an Ethiopian official (Acts 8.38), a Roman army officer (Acts 10.47,48), and a wealthy Greek woman (Acts 16.15). The apostle Paul wrote letters to local churches explaining that those who are baptized should make a break with their past life and become part of the people of faith (Rom 6.1-4; Col 2.11,12). Just as God saved Noah from the flood, and just as God raised Jesus from the dead, so God's new people are saved from the power of death, made acceptable to God, and welcomed into God's family when they are baptized (1 Pet 3.18-22).