John’s authority to baptize came ultimately from God, in fulfillment of his prophetic mission as “the voice of one crying in the wilderness” (Is 40:3; Lk 3:2–3). While John was indeed of priestly lineage (his father, Zechariah, was a Temple priest), the New Testament depicts his baptism primarily as a divine calling for repentance and preparation for the Messiah, rather than as a continuation of Old Testament priestly rites. Although the Old Covenant does not feature baptism as a formal sacrament, it does foreshadow purifying washings (see Lev 16:4, Num 19), which John’s ministry brought to a new stage by pointing to Christ. Finally, Jesus’ crucifixion by no means nullified His authority or any symbolic baptism He received; His Passion and Resurrection are what give true meaning and saving power to all Christian baptism.
John the baptist changed what was ritual cleansing to symbolic purification. Forgiveness of sins was a formal process requiring sacrificial offerings of animals and spilling of blood in the temple.
Even animal sacrifice was changed by Jesus to human sacrifice. Where he was the sacrificial lamb. All these changes were a perversion of the law which Jesus promised not to change or abolish.
Matthew 5:17
“Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them.
The priests had to be ritually clean (tahor) in order to serve at the tabernacle, and Israelites who had become ritually unclean (tamay) had to restore their situation with the passing of time and bathing their whole body in fresh, ritually clean (tahor) water, according to Leviticus 15.
Later, when the temple had been built, it was necessary for everyone to be immersed in a mikveh to become ritually clean before entering the temple. There are many ancient mikva’ot (plural of mikveh) to be seen in Jerusalem, and it is clear to see the two sets of steps for each one – a set of steps going down to the mikveh in an impure (tamay) state on one side, and on the other side, steps where the pilgrim will emerge fresh and ritually clean (tahor).
John had no authority from God. He was beheaded for his actions.