Wrong. Jesus himself never performed a baptism. He was baptized by John, who performed baptisms in the same fashion the Essenes had been practising for nearly a century already. The passage of Matthew 28:19, 20 (like many sayings attributed to Jesus in this gospel, also in Luke) is most likely a later adition to justify the practice of baptism by the christians. Actually, one of the most well established events of Jesus's life is also one of the things that caused more embarassments to the early christians: the fact that Jesus was baptized by John, thus being his disciple. THIS was an embarassing fact that the early christian writers had to get very creative in order to make it look otherwise. In turn, around those explanations, a whole new theology was then constructed.
I didn't mean he invented the ritual of baptism. Baptism is a ritual of Hinduism too.
But he gave a new meaning and function to it.
The baptism of Jesus (not in the sense it was performed directly by Him) is totally different from the baptism of John.
Yes, Jesus being baptized by John was not necessary and actually an apparent contradiction. That's why historians are comfortable to accept the historicity of this event. The existence of John is well documented outside the Bible. Actually he was much more popular than Jesus even after the crucifixion.