How can I explain the Trinity to a “Oneness” Pentecostal who says that Jesus is the only God and that the Father and the Holy Spirit are manifestations and not different persons of the Divinity? And how can I explain baptism in the name of the Father, Son, and Holy Ghost when this person insists on Acts 2:38, repent and be baptized in the name of Jesus? He claims the name of the three persons, or manifestations in his view, is Jesus.
In Matthew 28:19 Jesus explicitly commands his apostles to baptize in the name of the Trinity. This is where the Church received the Trinitarian formula. It wasn’t some pope’s idea. In Acts 2:38 the author is not presenting a liturgical formula. He is concerned with distinguishing Christ’s baptism from John the Baptist’s. The practice of the early Church was thoroughly Trinitarian. For further information, go to www.catholic.com/library/Trinitarian_Baptism.asp.