It is plain then that the baptism [ed. note: Two sentences about rebaptizing, wanting in some copies of the original, are omitted by Aquinas. This comment on St. Matthew has apparently passed successively through the hands of opposite controversialists upon the Arian question. It may be observed that the Eunomians rebaptized, and that the second General Council rejects their baptism.] of Christ does not undo the baptism of John, but includes it in itself; he who is baptized in Christ’s name hath both baptisms, that of water and that of the Spirit. for Christ is Spirit, and hath taken to Him the body that He might give both bodily and spiritual baptism.
John’s baptism does not include in it the baptism of Christ, because the less cannot include the greater. Thus the Apostle having found certain Ephesians baptized with John’s baptism, baptized them again in the name of Christ, because they had not been baptized in the Spirit: thus Christ baptized a second time those who had been baptized by John, as John himself declared he should, “I baptize you with water; but He shall baptize you with the Spirit.”
And yet they were not baptized twice but once; for as the baptism of Christ was more than that of John, it was a new one given, not the same repeated.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).