When Jesus told Nicodemus that he had to be born of water and spirit he meant that first a man must confess his sins and be baptized in water to show that he have repented and changed his life for God. That is why John the baptist had to come.,and Jesus followed that that same routine.And next comes the baptism of the Holy Ghost which God fills a person with, which is a new spirit known as born again, a new birth of the spirit man. A new spirit that will renew your mind. A clean fresh start. That is why he told them that indeed John the baptist baptized with water, but would baptize with fire, which is the holy ghost. No person can receive the holy spirit except by the laying on of hands of another person ,and to know you have been baptized in the holy spirit, the evidence is briefly speaking in tongues. Jesus did not leave us ignorant of that fact.. I know some people find that hard to believe ,but it is true. You see when you truly repent, God will cleanse your spirit from the sin within. ,and the burden of sin will be lifted, and you will fill like a changed person. But the baptism of the holy ghost have yet come by means of a spirit filled person. that is how he lets us know that we have been baptized in the holy spirit with the evidence of speaking in tongues.