1 John 5:6

Came by water and blood. The sense seems to be, by water, with which he ordered every one to be baptized and made Christians; 2ndly, by his blood shed on the cross for our redemption. (Witham) --- Blood: not only to wash away our sins by the water of baptism, but by his own blood. (Challoner) --- And it is the Spirit that testifieth that Christ [2] is the truth. By the Spirit, which is not here called the Holy Spirit, or the Holy Ghost, as in the next verse, is either meant the Spirit or soul of Christ, which dying he recommended into the hands of his Father, and which shewed that he was truly man, against Cerinthus, and some heretics of those times; or else it may signify the spirit of grace, given in this world to the faithful, in the same sense as St. Paul says, (Romans viii. 16.) that the Spirit himself giveth testimony to our Spirit, that we are the sons of God: and of which may be understood what is said here, (ver. 10.) He that believeth in the Son of God, hath the testimony of God in himself. (Witham)

[BIBLIOGRAPHY]

Quoniam Christus est veritas; in most Greek copies is now read, Greek: oti to pneuma esti e aletheia, quoniam Spiritus est veritas.