he said this about the spirit

The reason that the Baptism in the Holy Spirit is so important is because Jesus promised it to the disciples.   John wrote his Gospel after the day of Pentecost.  Jesus teaches in John 14 about the coming of the Holy Spirit.  There was a celebration day where Jesus was present.  On the last day, this happened:

John 7:37        On the last and most important day of the festival, Jesus stood up and cried out, “If anyone is thirsty, let him come to me and drink. 38 The one who believes in me, as the Scripture has said, will have streams of living water flow from deep within him.” 39 He said this about the Spirit. Those who believed in Jesus were going to receive the Spirit, for the Spirit had not yet been given because Jesus had not yet been glorified.

The Holy Spirit is available to all to help us with everything!  Praise God!