1 John 5:6

This (outo). Jesus the Son of God (verse 1 John 5 ). He that came (o elqwn). Second aorist active articular participle of ercomai, referring to the Incarnation as a definite historic event, the preexistent Son of God "sent from heaven to do God's will" (Brooke). By water and blood (di udato kai aimato). Accompanied by (dia used with the genitive both as instrument and accompaniment, as in Galatians 5:13 ) water (as at the baptism) and blood (as on the Cross). These two incidents in the Incarnation are singled out because at the baptism Jesus was formally set apart to his Messianic work by the coming of the Holy Spirit upon him and by the Father's audible witness, and because at the Cross his work reached its culmination ("It is finished," Jesus said). There are other theories that do not accord with the language and the facts. It is true that at the Cross both water and blood came out of the side of Jesus when pierced by the soldier, as John bore witness ( John 19:34 ), a complete refutation of the Docetic denial of an actual human body for Jesus and of the Cerinthian distinction between Jesus and Christ. There is thus a threefold witness to the fact of the Incarnation, but he repeats the twofold witness before giving the third. The repetition of both preposition (en this time rather than dia) and the article (twi locative case) argues for two separate events with particular emphasis on the blood ("not only" ouk monon, "but" all) which the Gnostics made light of or even denied. It is the Spirit that beareth witness (to pneuma estin to marturoun). Present active articular participle of marturew with article with both subject and predicate, and so interchangeable as in John 3:4 . The Holy Spirit is the third and the chief witness at the baptism of Jesus and all through his ministry. Because (oti). Or declarative "that." Either makes sense. In John 15:26 Jesus spoke of "the Spirit of truth" (whose characteristic is truth). Here John identifies the Spirit with truth as Jesus said of himself ( John 14:6 ) without denying personality for the Holy Spirit.