I was wondering why, seeing as baptism was not performed in Old Testament times, John the baptist started to baptize people to symbolize their repentance. I know in the New Testament Jesus instructs people to be baptized in the name of the Father, Son and Holy Spirit, but John came before Jesus.
John’s baptism was an adaptation of the mikvah, or ritual immersion bath, that had been part of Jewish life for generations and symbolized a spiritual cleansing. It was part of the preparation for undertaking a new beginning. Jewish men took a mikvah each Sabbath in preparation for the new week. Women took a mikvah after each monthly period as a spiritual cleansing. On Yom Kippur the High Priest took 7 mikvot (plural of mikvah) during the ceremonies in preparation for entering the Holy of Holies. Jesus came to John for a mikvah at the beginning of His ministry.
The reason John had people take a mikvah was to show that they had changed their minds (repented) about their need for a Savior and were taking a new direction regarding their salvation. No longer would they focus on keeping the Law but would look instead to the coming redeemer whose arrival John was announcing. Today, baptism is no longer an act of spiritual cleansing in preparation for a new direction, but a public declaration that the spiritual cleansing has already happened and the new direction has been taken.