Matthew 3

In Matthew 3 John the Baptist is baptizing people in the Jordan river. Jewish law had two ordinances that would resemble what we call baptism - Priestly Purification, and Proselyte Baptism. These were cleansing rituals performed according to strict traditional guidelines. John was baptizing people and hearing their confession of sins, so this probably upset the Pharisees and Sadducees because it resembled their rituals but was being done outside of their supervision. When John called them a brood of vipers he was basically equating them to the serpent in Genesis, so it was among the greatest of insults he could hurl at them.

And John says that One more powerful than him will come baptizing with the Holy Spirit and with fire. That speaks to me of the first (Holy Spirit) and second (fire) comings of Jesus. Jesus came first to save His people through faith and the impartation of the Holy Spirit. Jesus will come again to judge and destroy those who refuse Him.

Jesus gets baptized to "fulfill all righteousness" and I see this as Him redefining the priestly practices I mentioned before. Instead of making baptism about the adherence to temple law, He now redefined it as a public confession of faith in Him. He did a similar thing with the Passover meal - taking it from being a Jewish ordinance and making it an ordinance for all who believe in Him. In doing so He fulfilled the purpose of the Old Jewish ordinance and expanded it to something new that includes all people who believe in Him. And it was not merely an earthly action, it was an action that was attended by the Holy Spirit and God the father as well as the Son. The whole triune being of God was present at Jesus's baptism.