He will baptize you with the Holy Spirit and fire. In the New Testament mention is made of three baptisms. There is John's baptism in the water of repentance. There is baptism in water, in the name of Jesus. There is baptism with Holy Spirit.
Baptism is a rich idea.
As well, a covenant relationship in Christ is entered into, together with His Body, the Church. Baptism is the sign of a change of status, of position and so of relationship, with our God. This is the fundamental question. Creation, and the acts of salvation through Moses and in Jesus, are the big examples. He takes initiatives usually before people are fully able to understand the implications.