Baptism Is an Act of God

There is one body and one Spirit, just as you were called in one hope of your calling; one Lord, one faith, one baptism; one God and Father of all, who is above all, and through all, and in you all. (Eph 4:4–6)

The rite of baptism, when it finally occurs, is not a mere seal set on the initiate as a sign of the successful performance of a series of penitential acts for purification, as Basil summarized the baptism of Moses, nor is it an external washing for forgiveness of sins as with John the Baptist, but it is rather a divine act involving Father, Son, and Holy Spirit.*

John the Baptist, than whom there is no greater among them that are born of woman [cf. Matt. 11:11], likewise bears witness in the words: He must increase, but I must decrease [John 3:30]; and again: I indeed baptize you in water unto repentance, but he baptizes you in the Holy Spirit and fire [Matt. 3:11], and so in many other places. The Holy Spirit is as far superior to water as he who baptizes in the Holy Spirit obviously is to him who baptizes in water. And this is true also of the baptism itself. [Basil, Concerning Baptism 1.2.4]

Baptism is an act of God the Holy Spirit in the believer.

Timothy P. McConnell, Illumination in Basil of Caesarea’s Doctrine of the Holy Spirit

* McConnell is trying to harmonize the biblical divine work being accomplished at baptism with personal belief displayed through Basil’s requirement of catechism and moral transformation prior to baptism.