Tertullian, On Baptism 6
We do not receive the Holy Spirit in the waters; rather, once we have been cleansed in the water under the Angel, we are prepared for the Holy Spirit. This pattern also appeared earlier. Just as John went before the Lord as a forerunner to prepare his ways, so the Angel, the arbiter of Baptism, clears the way for the coming Holy Spirit through the washing away of sins—a washing that faith obtains, sealed in the Father, the Son, and the Holy Spirit. If every word stands on the testimony of three witnesses, how much more does the very number of the divine names guarantee our confident hope, now that we possess those same three as guarantors of our faith and sponsors of our salvation through the blessing? And when both the profession of faith and the pledge of salvation are made under those three, the mention of the Church becomes unavoidable; for where the three are—that is, the Father, the Son, and the Holy Spirit—there is the Church, which is the body of the three.
Latin
Non quod in aquis Spiritum sanctum consequamur; sed in aqua emundati sub Angelo, Spiritui sancto praeparamur. Hic quoque figura praecessit. Sic enim Joannes ante praecursor Domini fuit, praeparans vias ejus: ita et Angelus Baptismi arbiter superventuro Spiritui sancto vias dirigit ablutione delictorum, quam fides impetrat, obsignata in Patre, et Filio, et Spiritu sancto. Nam si in tribus testibus stabit omne verbum, quanto magis, dum habemus per benedictionem eosdem arbitros fidei, quos et sponsores salutis, sufficit ad fiduciam spei nostrae etiam numerus nominum divinorum? Cum autem sub tribus, et testatio fidei, et sponsio salutis pignerentur, necessario adjicitur Ecclesiae mentio; quoniam ubi tres, id est Pater et Filius et Spiritus sanctus, ibi Ecclesia, quae trium corpus est.