This is he who came by water and blood—Jesus Christ; not by the water only but by the water and the blood. And the Spirit is the one who testifies, because the Spirit is the truth.
6 This is he that came That our faith may rest safely on Christ, he says the real substance of the shadows of the law appears in him. For I doubt not but that he alludes by the words water and blood to the ancient rites of the law.
The faith of the Christian believer (or the believer in Christ) being thus mighty and victorious, it had need to be well founded, to be furnished with unquestionable celestial evidence concerning the divine mission, authority, and office of the Lord Jesus; and it is so; he brings his credentials along with him, and he brings them in a way by which he came and in the witness that attends him.
Commenting on 1 John 5:6-9
This is he that came by water and blood, even Jesus Christ,.... By "water" is not meant the ablutions or washings of the ceremonial law; Christ came not by these, but to make an end of them; his blood, which cleanseth from all sin, being the antitype, and so the fulfilling end of them: nor the purity of his nature, life, and conversation; though he...