John baptized with a baptism of repentance and urged the people to believe in the one who was to come after him, Jesus Christ. As Paul made his way through Ephesus in the course of his evangelization, he broached on the subject of the Holy Spirit, which to his surprise, the Ephesians were hearing for the first time. The Ephesians were just as surprised as St. Paul on hearing that there is something called the Holy Spirit, and upon further inquiry, they reveal to Paul that the only thing they had received was a baptism of John. It is a revelation that alarms Paul who then proceeds to explain to them the necessity of being baptized in the name of Jesus: “The baptism of John which you all received was just the beginning since it is a baptism of repentance. In order to receive the Holy Spirit- and you very much need the Holy Spirit- you have to be baptized in the name of Jesus.” Does this mean that John’s baptism was inefficient? Not really. However, as Paul further explains, John’s baptism was preparatory and transitory. Its purpose was to prepare the people for the advent of God’s kingdom, the in-breaking of which was the appearance on the scene by Jesus. 
The repentive nature of John’s baptism did not mean that the people to whom John preached were worse sinners than we are today. Rather, it was a means of easing the people into another epoch, an epoch in which God was to be revealed to all in the person of Jesus Christ (hence the transitory nature of John’s baptism). As such, John’s baptism was not meant to last forever. It was to be replaced or rather superseded by the baptism of the Holy Spirit, that is, baptism in the name of Jesus Christ. While the nature of baptism remained the same (both involved the renunciation of sins and some form of washing/ablution), the purpose changed. Baptism in the name of Jesus is functionary, that is, baptism in the name of Jesus calls upon those who receive it to join Jesus in ushering in the kingdom. After baptism in the name of Jesus, one is sent forth to proclaim the kingdom, an activity that cannot be successful if one doesn’t have the Holy Spirit. This is why it was necessary for the members of the Ephesian church to be baptized in the name of Jesus. Like Paul, they too were to become proclaimers of the kingdom.