That is the question raised about the beliefs of the people from Ephesus who had been baptized by John the baptizer (Acts 19:3). John preached the Gospel: Jesus, he said, is the Lamb of God” who had come to “take away the sins of the world.” And he plainly stated that (in contrast to his water baptism) Jesus would baptize “with the Holy Spirit as well.”
John stood at the razor’s edge of the two covenantal periods. He looked into the future era, but remained the other, Old Testaments side of the divide. His message was “repent because the kingdom of God is near.” It was largely negative, and, like his predecessor, Elijah, whose clothing and mission were similar(though disappointed), was seeking a national repentance such as there had been in Nineveh under Jonah. Though many were baptized by him and his disciples, they were also directed to the more positive baptism that would take place under Jesus.
Jesus’ baptism—so far as it went—wasn’t merely a recognition of the cleansing of sins by repentance in order to avoid the: wrath soon to come (“the axe is laid at the foot of the tree; His fan is in His hand” ready to strike down the unrepentant Jews and throw them into the fire). It was a positive message as well, declaring the good news of Christ’s sacrificial death.
The positive message of Jesus also spoke of the coming of One Who would “guide” the apostles into “all truth,” Who would give people a new heart to believe through a “new birth, and who would die in the place of guilty sinners, bearing their punishment in order to accomplishment it. It would all happen shortly after John’s death and the resurrection and ascension of the one’s whom He announced.
Since the period was one of change, and these disciples of John had not even heard of the Holy Spirit as a part of the message of good news, the question was pertinent: “into what , then, were you baptized?” They could only answer that they were baptized into the negative message of repentance preached by John the Baptizer (he was not a “Baptist” in the modern sense of the term).
Although John’s baptism was valid, correct, and God-ordained, it was not sufficient to replace Christian baptism. So these disciples of John were baptized into the separated, and wholly distinct Christian baptism to which Jesus’ Name was attached, and to which the coming of the Spirit was appended, at this later point in Gospel history. The key this is to recognize in the question above is its import—the meaning of one’s baptism is crucial to determining its validity: “Into what” (i.e., to what end, or purpose, or effect) were you baptized?”) Unless that intention it has in view the baptism of Jesus in water and the Spirit, it is not valid baptism. If it has some purpose other than the biblically-stated one, it is invalid. So, if one is baptized into the Roman Church for cleansing from original sin, for instance, (and into the cults whose baptisms may have unscriptural ends) his baptism isn’t satisfactory. Even though John’s was God-given, because it was not Christian baptism and had a different end—by repentance to prepare men for the Coming of Christ—it was not sufficient. The apostles, as we do. baptism p[eople into Christ, with the New Testament fullness of its meaning.
A question to ask a new convert is not only whether he has been baptized, but whether or not the intent of the baptism was fully and truly Christian—or something else.