Now it was the day of Preparation, and the next day was to be a special Sabbath. Because the Jewish leaders did not want the bodies left on the crosses during the Sabbath, they asked Pilate to have the legs broken and the bodies taken down. The soldiers therefore came and broke the legs of the first man who had been crucified with Jesus, and then those of the other. But when they came to Jesus and found that He was already dead, they did not break His legs. Instead, one of the soldiers pierced Jesus’ side with a spear, bringing a sudden flow of blood and water. (John 19:31–34)
When I was a child, I was puzzled by the above description. The whole thing about water coming out of the chest was mysterious to me. Later on, I learned about some of the religious symbolism of the mix of blood and water; the theological interpretation of the water pouring out of Jesus’ chest is tied into the baptism.
But how is it possible that water drained together with blood after the stab wound to the chest? Is this water some kind of literary religious aid to explain baptism?
The answer is that Jesus developed heart failure due to respiratory failure. It is not unusual in patients with heart failure to develop accumulation of fluid in body cavities. It is called effusions.
In this case, Jesus developed a pericardial effusion which is water around the heart in what is called the pericardial space or sac. The spear pierced several layers of tissue until reaching the pericardial sac where encountered the blood and the water.
This is a sound physiological explanation to the “sudden flow of blood and water” as described by John.
What do you think? Does this make more sense to you now?