Fr. Robert Barron, in a post on Word on Fire says that our Baptism is like a “grafting to Christ” through the sacrament. Then what was it to the people John the Baptist baptized prior to Christ’s death? Was this something like a Jewish baptism?
In Judaism baptism was a symbol of repentance and a sign of purification of the body. As the Jewish Encyclopedia notes:
Accordingly, Baptism is not merely for the purpose of expiating a special transgression, as is the case chiefly in the violation of the so-called Levitical laws of purity; but it is to form a part of holy living and to prepare for the attainment of a closer communion with God. This thought is expressed in the well-known passage in Josephus in which he speaks of John the Baptist (“Ant.” xviii. 5, § 2): “The washing would be acceptable to him, if they made use of it, not in order to the putting away of some sins, but for the purification of the body; supposing still that the soul was thoroughly purified beforehand by righteousness.”
In Jewish baptism the sins of the individual have already been spiritually forgiven, the baptism is a sign of that and also serves the purpose of purifying the body from those sins. This was the baptism that John the Baptist practiced.
In Christian baptism, the sacrament is what forgives sins and because in configures the individual to Christ it can only be received once unlike the baptism of John which could be repeated as often as necessary.