On Baptism by Tertullian
Chapter IV.--The Primeval Hovering of the Spirit of God Over the Waters Typical of Baptism. The Universal Element of Water Thus Made a Channel of Sanctification. Resemblance Between the Outward Sign and the Inward Grace.
But it will suffice to have thus called at the outset those points in which withal is recognised that primary principle of baptism, -- which was even then fore-noted by the very attitude assumed for a type of baptism, -- that the Spirit of God, who hovered over (the waters) from the beginning, would continue to linger over the waters of the baptized. But a holy thing, of course, hovered over a holy; or else, from that which hovered over that which was hovered over borrowed a holiness, since it is necessary that in every case an underlying material substance should catch the quality of that which overhangs it, most of all a corporeal of a spiritual, adapted (as the spiritual is) through the subtleness of its substance, both for penetrating and insinuating. Thus the nature of the waters, sanctified by the Holy One, itself conceived withal the power of sanctifying. Let no one say, |Why then, are we, pray, baptized with the very waters which then existed in the first beginning?| Not with those waters, of course, except in so far as the genus indeed is one, but the species very many. But what is an attribute to the genus reappears likewise in the species. And accordingly it makes no difference whether a man be washed in a sea or a pool, a stream or a fount, a lake or a trough; nor is there any distinction between those whom John baptized in the Jordan and those whom Peter baptized in the Tiber, unless withal the eunuch whom Philip baptized in the midst of his journeys with chance water, derived (therefrom) more or less of salvation than others. All waters, therefore, in virtue of the pristine privilege of their origin, do, after invocation of God, attain the sacramental power of sanctification; for the Spirit immediately supervenes from the heavens, and rests over the waters, sanctifying them from Himself; and being thus sanctified, they imbibe at the same time the power of sanctifying. Albeit the similitude may be admitted to be suitable to the simple act; that, since we are defiled by sins, as it were by dirt, we should be washed from those stains in waters. But as sins do not show themselves in our flesh (inasmuch as no one carries on his skin the spot of idolatry, or fornication, or fraud), so persons of that kind are foul in the spirit, which is the author of the sin; for the spirit is lord, the flesh servant. Yet they each mutually share the guilt: the spirit, on the ground of command; the flesh, of subservience. Therefore, after the waters have been in a manner endued with medicinal virtue through the intervention of the angel, the spirit is corporeally washed in the waters, and the flesh is in the same spiritually cleansed.