The message of John the Baptist is that there is a new era coming. In this new era everything is going to be turned upside down so you’d better prepare yourself through repentance and readying yourself for a new era by being ritually cleansed as a sign of righteousness.
Matthew 3:11 “I baptize you with water for repentance. But after me will come one who is more powerful than I, whose sandals I am not fit to carry. He will baptize you with the Holy Spirit and with fire.”