Commentary on 1 John 5:5-13 
Today’s reading is taken from the Third Part of the Letter – the Source of Love and Faith and speaks about the source of Faith. To understand this reading we also need to know that John is speaking in the context of Gnostic teachings which said that the Spirit of God entered into Jesus only at his baptism and left him before his death on the cross. John begins today’s passage by asking, “Who can overcome the world?” He means this not in any triumphalist or dominating way about the world in general but rather using ‘world’ in the sense of asking who is the one who has the ability to overcome the evil tendencies with which our lives are surrounded. The implication is that it is someone who directly came to grips with the world, not an outsider.
The answer is that it is the one who has total faith in Jesus as the Son of God. Faith in Jesus who not only came through the water of his baptism but “in water and in blood” where “blood” signifies Jesus’ death on the cross. All of this is testified to by the Spirit who, with the testimony of the water and blood, which symbolically flowed from the breast of the dead Jesus, form one single witness to the identity and the work of Jesus.
John is reacting to the heretics of his day (especially Cerinthus) who said that Jesus was born only a man and remained so until his baptism. At that time, they maintained, the Christ (the Son of God) descended on the human Jesus, but left him before his suffering on the cross – so that it was only the man Jesus who died. Throughout this letter John has been insisting that Jesus Christ is God as well as man (1:1-4; 4:2; 5:5). He now asserts that it was this God-man Jesus Christ who came into our world, was baptised and died. Jesus was the Son of God not only at his baptism but also at his death (v.6b). This truth is extremely important, because, if Jesus died only as a man, his sacrificial atonement (2:2; 4:10) would not have been sufficient to take away the guilt of man’s sin. (New International Version Study Bible)
It is John in his Gospel who tells us that when the dead Jesus’ side was pierced, there came out blood and water – signifying both his sacrificial death and his Baptism in the Spirit. “One of the soldiers, however, plunged his spear into Jesus’ side and at once blood and water poured out” (cf. John 20:34). It is interesting that he then adds a parenthesis which makes more sense in the Gnostic context: “The one who saw this happen has spoken of it, so that you may also believe. What he said is true, and he knows that he speaks the truth” (Jn 20:35). In other words, the Person who died was the God-made-man, something denied by the Gnostics.
So, “there are three witnesses – the Spirit, water and blood; and the three of them coincide”. The Spirit pervades the life and death of Jesus. He was born in the Spirit, baptised in the Spirit and died in the Spirit – the Spirit of God.
The blood and water were the ‘evidence’ for the original eyewitnesses but they are also the witness for all Christians as the type of the baptism and the sacrificial death of Jesus which are operative in our own lives.
For us, it is essential to our understanding of Jesus that it was the incarnate Son of God who died on the cross otherwise his death would not have had its redemptive and atoning effect.
To believe in Jesus as the Son of God is to accept this testimony as that of God himself. Not to believe in the witness that Jesus has given by his life and death is to make a liar of God. For “God gave us eternal life, and this life is in his Son”. And so, “whoever possesses the Son possesses life”. This is not merely a statement to be accepted. It is a reality that can be experienced and should be experienced. And it is in the experience that we know its truth.
In the Gospel Jesus tells us again and again that he has come to give life to the world and we know from experience that all those who commit themselves to Jesus and his Gospel experience this life. That life is open to every one of us provided we, in a spirit of total trust and faith, surrender ourselves to Jesus as Lord.
But it is not given willy-nilly nor is it forced on us: we have to open our hearts and allow God’s love and life to flow in.