John's Baptism

Matthew 3:1-6 (ESV)
In those days John the Baptist came preaching in the wilderness of Judea, [2] "Repent, for the kingdom of heaven is at hand." [3] For this is he who was spoken of by the prophet Isaiah when he said,

"The voice of one crying in the wilderness:
'Prepare the way of the Lord;
make his paths straight.' "

[4] Now John wore a garment of camel's hair and a leather belt around his waist, and his food was locusts and wild honey. [5] Then Jerusalem and all Judea and all the region about the Jordan were going out to him, [6] and they were baptized by him in the river Jordan, confessing their sins.

“Repent, for the kingdom of heaven is at hand.” “ and they were baptized by him in the river Jordan, confessing their sins.”
John was sent to prepare the way. He preached law. To be sure he had moments where the gospel shined through as at no other time, instances where he would cry out “Behold, the Lamb of God who takes away the Sin of the World!” But he was sent to prepare people for that Gospel as it came in Jesus Christ. So he preached law to expose the people to their sins. He could be harsh. He lived the law as much as he preached it. In the end it would be that side of God’s double edged sword that would kill him, just as he lived by it. He lived by the law, and he died by the law. In the meantime he preached the law relentlessly.
So the people heard, and they repented of their sins, they were baptized confessing their sins. This is what John’s baptism was about, repenting of sins, confessing sins. This is not the same thing as Christian baptism. John himself, it will be shown later, sharply distinguished between what he was doing and what Christ would do when it came to baptizing.
Yet with every baptism there is a confession of sins. If we didn’t have sins than we would not need Christ to baptize us, to forgive our sins in baptism, to save us in baptism, but with Christian baptism there is the promise of forgiveness, the promise of salvation, there is Christ’s own hand giving us faith, strengthening faith, kindling faith.
But it must also be noted, John is baptizing believers. These men and women that come to him from all over the country side, they are believers. They are children of the Old Testament. They are circumcised according to the law, but also by the grace of God. They could not repent without believing. For that is really impossible. The first commandment demands faith. To repent of sin, is to repent of breaking the first commandment. It is from a lack of fear, love and trust in God above all things, that all of our sin comes from. It is the other gods that we love more than God, fear more than God, trust more than God, ourselves, our family, our friends, money, etc. that we put above God that drive us to sin, to break the other nine commandments. So to repent of sin, to turn away from sin, is to turn to God, to be given faith, to believe that he will save us.
These men were believers, but then so are all who are baptized, young or old, infant or senior, and faith is always a miracle, always a gift of God.