What does Acts 19:4 mean?

John the Baptist was the last of the Old Testament prophets. Malachi, the last book of the Old Testament, prophesied his coming (Malachi 3:1). John preached that people needed to repent from their sin and turn back to God, thus returning "the hearts of fathers to their children and the hearts of children to their fathers" (Malachi 4:6). John's ministry was extremely popular—so much so that although John publicly attacked the morality of the Pharisees, the Pharisees still avoided criticizing him in public three years after his death (Matthew 3:7–10; Mark 11:27–33).

John preached along the Jordan River, less than twenty miles east of Jerusalem. His spot was at or near the route Jews took from Galilee to Jerusalem when they came for sacrifices or feasts. When people heard and agreed with his message, he—or his disciples—baptized them. The people publicly announced that they agreed with John's message of repentance (Luke 3:1–6).

But John also said, "I baptize you with water for repentance, but he who is coming after me is mightier than I, whose sandals I am not worthy to carry. He will baptize you with the Holy Spirit and fire" (Matthew 3:11). As Malachi said, John came to call people to repentance, but he also came to prepare the way for people to accept Jesus and His offer of salvation (Malachi 3:1; 4:5–6; Isaiah 40:3–5; John 1:23).

The twelve men in Ephesus understood and accepted John's message of repentance. Paul explains to them that John pointed to Jesus of Nazareth. John told his followers he would decrease so that Jesus could increase (John 3:30). Even here, decades after Jesus ascended into heaven, this is still happening. John's message prepared these men to recognize Jesus as their Savior.