The answer
The baptism of St. John the Baptist is a baptism of repentance, whereas the baptism of Christ is for the forgiveness of sin. St. John's baptism bound its subjects to repentance, and not to the faith of Christ. It was not administered in the name of the Trinity. Therefore those whom John baptized had to be re-baptized by Paul (Acts 18:24; 19:7).St. Augustine says "Those who were baptized with John's baptism needed to be baptized with the baptism of our Lord." In his 'Contra Faust' he says, "our sacraments are signs of present grace, whereas the sacraments of the Old Law were signs of future grace. Wherefore the very fact that John baptized in the name of one who was to come shows that he did not give the baptism of Christ, which is a sacrament of the New Law."
St. John Chrysostom in Homily 4 on the Holy Book of St. Matthew says, "Since, when John said, 'I ought to be baptized by Thee,' Christ answered, 'Suffer it to be so now': it follows that afterwards Christ did baptize John." Moreover, he asserts, "This is distinctly set down in some of the apocryphal books." St. Jerome says on Matthew 3:13, that, "as Christ was baptized in water by John, so had John to be baptized in the Spirit by Christ."
Answered by His Eminence Metropolitan Youssef (opens in a new tab)