When Paul came to Ephesus, he found some "some disciples" (Acts 19:1 NKJV). The men were "about twelve in all" (Acts 19:7). Paul questioned the men about the Holy Spirit and learned that they were deficient in the knowledge of the plan of redemption (c.f. Acts 19:2). Paul asked, "Into what then were you baptized" (Acts 19:3)? They said that they had been baptized into "John's baptism" (Acts 19:3). Apollos, for example, "knew only the baptism of John" until he was taught (Acts 18:25-26).
What was John's baptism? The baptism of John was very similar to baptism in the name of the Lord. First, John's baptism required belief (c.f. Acts 19:4). Second, John's baptism required repentance (Matt. 3:8, 11). Third, John's baptism required confession (Matt. 3:6). Fourth, John's baptism was immersion in water (Mark 1:5, 9-10; John 3:23). Fifth, John's baptism was "for the remission of sins" (Mark 1:4; Luke 3:3).
What was John's purpose? John appointed to prepare the people for the Lord Jesus Christ (Luke 1:16-17, 76-79; John 1:6-8). He preached concerning the Lamb of God (John 1:28-29), the kingdom of heaven (Matt. 3:1-2), and the unquenchable fire of Judgment (Matt. 3:10-12). Those who believed and obeyed the message of John, would be a part of the "people prepared for the Lord" (Luke 1:17). They would be "prepared" to receive the remission of sins in the blood of Christ (Matt. 26:28). They would be "prepared" to be added to the kingdom by the Lord, once the kingdom was established on the Day of Pentecost (Acts 2:1, 41, 47).
The men of Ephesus said that they had been baptized into "John's baptism" (Acts 19:3). Into what are we baptized today? Paul told the Romans that we are "baptized into Christ Jesus" (Rom. 6:3). He wrote to the Corinthians, "For by one Spirit we were all baptized into one body" (1 Cor. 12:13), "the body of Christ" (1 Cor. 12:27). The "one body" is also called the church (Eph. 4:4; Col. 1:18). Paul told the Christians of Galatia, "For you are all sons of God through faith in Christ Jesus. For as many of you as were baptized into Christ have put on Christ" (Gal. 3:26-27).
The apostle Peter also taught the importance of baptism on the Day of Pentecost. He said, "Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit" (Acts 2:38). "Then those who gladly received his word were baptized; and that day about three thousand souls were added to them" (Acts 2:41). "And the Lord added to the church daily those who were being saved" (Acts 2:47).
There is "one baptism" in effect today (c.f. Eph. 4:5). Peter commanded the Jews, "be baptized in the name of Jesus Christ" (Acts 2:38). He commanded the Gentiles to be "baptized in the name of the Lord" (Acts 10:46-48). Philip preached Christ at Samaria and those who believed were "baptized in the name of the Lord Jesus" (Acts 8:16). He also preached Jesus to the Ethiopian eunuch. After confessing Christ, the eunuch was baptized in water (Acts 8:36-39). The "one baptism" is the one and same baptism commissioned by Christ (Matt. 28:18-20; Mark 16:15-16), preached by the disciples, administered by men, and submitted to by believers of every nation. Peter wrote, "There is also an antitype which now saves us; baptism" (1 Pet. 3:21).
The men of Ephesus were not baptized into John's baptism while it was still in effect. Once they heard Paul concerning the Lord Jesus (Acts 19:4), "they were baptized in the name of the Lord Jesus" (Acts 19:5). These disciples became Christians. Will you become a Christian today?