Christ is Himself present in Baptism, so that we need not consider the person of His ministers. A brief explanation of the confession of the Trinity as usually uttered by those about to be baptized.
26. Is there, then, here any room left for doubt, when the Father clearly calls from heaven in the Gospel narrative, and says: “This is My beloved Son, in Whom I am well pleased”? When the Son also speaks, upon Whom the Holy Spirit showed Himself in the likeness of a dove? When the Holy Spirit also speaks, Who came down in the likeness of a dove? When David, too, speaks: “The voice of the Lord is above the waters, the God of glory thundered, the Lord above many waters”? When Scripture testifies that at the prayer of Jerubbaal, fire came down from heaven, and again, when Elijah prayed, fire was sent forth and consecrated the sacrifice.
27. Do not consider the merits of individuals, but the office of the priests. Or, if you look at the merits, consider the priest as Elijah. Look upon the merits of Peter also, or of Paul, who handed down to us this mystery which they had received of the Lord Jesus. To those [of old] a visible fire was sent that they might believe; for us who believe, the Lord works invisibly; for them that happened for a figure, for us for warning. Believe, then, that the Lord Jesus is present at the invocation of the priest, Who said: “Where two or three are, there am I also.” How much where the Church is, and where His Mysteries are, does He vouchsafe to impart His presence!
28. You went down, then (into the water), remember what you replied to the questions, that you believe in the Father, that you believe in the Son, that you believe in the Holy Spirit. The statement there is not: I believe in a greater and in a less and in a lowest person, but you are bound by the same guarantee of your own voice, to believe in the Son in like manner as you believe in the Father; and to believe in the Holy Spirit in like manner as you believe in the Son, with this one exception, that you confess that you must believe in the cross of the Lord Jesus alone.
Source: On the Mysteries (New Advent)