John Calvin Commentary 1 John 5:6

"This is he that came by water and blood, [even] Jesus Christ; not with the water only, but with the water and with the blood." — 1 John 5:6 (ASV)

This is he that came. So that our faith may rest safely on Christ, he says that the real substance of the shadows of the law appears in him. For I have no doubt that he alludes with the words water and blood to the ancient rites of the law.

The comparison, moreover, is intended for this purpose: not only that we may know that the Law of Moses was abolished by the coming of Christ, but also that we may seek in him the fulfillment of those things which the ceremonies previously typified.

And though they were of various kinds, yet under these two the Apostle signifies the whole perfection of holiness and righteousness. For by water all filth was washed away, so that people might come before God pure and clean, and by blood expiation was made and a pledge given of a full reconciliation with God. However, the law only adumbrated by external symbols what was to be truly and fully performed by the Messiah.

John then aptly proves that Jesus is the Christ of the Lord previously promised, because he brought with him that by which he wholly sanctifies us.

Indeed, regarding the blood by which Christ reconciled God, there is no doubt; but how he came by water can be questioned. However, it is not probable that the reference is to baptism.

I certainly think that John presents here the fruit and effect of what he recorded in his Gospel account; for what he says there—that water and blood flowed from the side of Christ—is undoubtedly to be deemed a miracle.

I know that such a thing can happen naturally with the dead. However, it happened through God’s purpose that Christ’s side became the fountain of blood and water, so that the faithful may know that cleansing (of which the ancient baptisms were types) is found in him, and that they might know that what all the sprinklings of blood previously prefigured was fulfilled.

We discussed this subject in greater detail in Hebrews 9 and 10.

And it is the Spirit that beareth witness. He shows in this clause how the faithful know and feel the power of Christ—namely, because the Spirit renders them certain.

And so that their faith might not waver, he adds that full and genuine firmness or stability is produced by the testimony of the Spirit. He calls the Spirit truth because His authority is indubitable and should be abundantly sufficient for us.