1 John 5:6b

This is the one who came by water and blood—Jesus Christ. He did not come by water only, but by water and blood. And it is the Spirit who testifies, because the Spirit is the truth.

(v6, NIV)

What does the blood refer to? Well I think most of us if not all of us know what blood is. We cut ourselves sometimes and we bleed. Blood flows through our veins and it is what our heart pumps. I'm not an expert on the matter, nor do I know the detailed intricacies of how the body works, but I think I have a general understanding of what blood is. However, "blood" in this case is different.

But if we walk in the light, as he is in the light, we have fellowship with one another, and the blood of Jesus, his Son, purifies us from all sin.

(1 John 1:7, NIV)

Staying within the bounds of 1 John, we find the word "blood" in the first chapter. What does the blood of Jesus do? It is his blood that purifies us from all sin. Jesus' blood was shed on that cross and it was for us. We have sin and we are so deathly sinful. We are so dirty that we cannot come before a holy, righteous, pure and spotless God. But it is Jesus' blood that purifies us from our sins. He took upon himself our sins and God's rightful wrath that was due to us was poured out upon Jesus. It is his blood that cleanses us from our sins.

Jesus came by water and blood. It wasn't just by water, to bring cleansing and the cleansing work of the Holy Spirit, but it was also by blood. He came to shed his blood as an atoning sacrifice for us. Both work hand in hand are both are required. Someone can't claim to have the Holy Spirit, but not acknowledge the work of Jesus' sacrifice on the cross. In addition, people can't claim to be saved through Jesus' blood but not have the Holy Spirit. The water and the blood are both necessary parts for the child of God and they are both part of what Jesus came by.