The first reading describes a Christian baptism, contrasting it with the baptism administered by John the Baptist. It says that John “baptized with a baptism of repentance, telling the people to believe in Jesus.”
John’s baptism was a sincere gesture of repentance but its value for the individual consisted only in it ability to make him or her sorry for sins and anxious to meet with the Savior. Its worth was emotional. It was not a Sacrament.
The Sacrament of Baptism, what Luke calls Baptism in the Spirit, has the force of enrolling one in the Christian family. Without needing any conscious reaction from the one being baptized (he or she might even be asleep) the Sacrament of Baptism takes its effect.
Neither does its effect depend on the mental state of the one conferring the Sacrament. He need not even be a believer. The Sacrament takes its effect if the water is poured as the one pouring says, “I baptize you in the name of the Father, Son, and Holy Spirit.”