“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. For there are three that testify: the Spirit and the water and the blood; and these three agree. If we receive the testimony of men, the testimony of God is greater, for this is the testimony of God that he has borne concerning his Son. Whoever believes in the Son of God has the testimony in himself. Whoever does not believe God has made him a liar, because he has not believed in the testimony that God has borne concerning his Son. And this is the testimony, that God gave us eternal life, and this life is in his Son. Whoever has the Son has life; whoever does not have the Son of God does not have life.” (1 John 5:6–12)
To be honest, this isn’t the most straightforward passage in John’s letter! What on earth is all this business about water and blood, and all this emphasis on testimony?
Often when reading the letters in the New Testament, you need to piece together what caused the letter to be written in the first place. You might remember a few chapters back we came across the false teachers (called “antichrists”), and it would seem that John is addressing their beliefs now.
It would seem that these people taught that Jesus came by “water only” and not by blood. Now, if we understand that by “water” we are supposed to think of Jesus’ baptism, and that “blood” refers to his crucifixion, we get the idea that these “antichrists” were teaching that Jesus didn’t really die. They were happy to say that he was baptised, and that the Holy Spirit came upon him, but that he really died? Nope.
Now why would they think that? There were early heretics who taught that Jesus didn’t really become human. He just seemed to be human. He was fully God, but not fully man. These teachers held that since human beings sin, it is impossible for a holy, divine being to be human too. The two natures just can’t get on. John, though, was adamant that Jesus “became flesh and dwelt among us” (John 1:14). He really was fully human and fully divine.
This means that when we pray, we pray to a God who knows what it is to be human. It means that he - as a human - can pay for the sin which we - as humans - have committed. As divine, he has “eternal life” to grant us, and can fully bear all the punishment which God places upon his shoulders for our sin. Both are needed, and so John insists that both are present.
This might seen like technical theological arguments, and they are. They do have consequences though, which is why the church took so much time to craft the creeds we say. We should not dismiss their teaching lightly, for if we do we begin to stray into religions which are not Christian.