Why did blood and water flow from Jesus' side when he was pierced?

The moment when a Roman soldier pierced Jesus’ side with a spear, causing blood and water to flow out, is a profound and deeply symbolic event recorded in the Gospel of John. This occurrence is not only historically significant but also theologically rich, offering insights into the nature of Jesus' sacrifice and its implications for humanity.

In John 19:34, we read, “But one of the soldiers pierced his side with a spear, and at once there came out blood and water.” This verse has intrigued theologians, medical professionals, and believers for centuries. To understand why blood and water flowed from Jesus' side, we need to consider both the physiological and theological dimensions.

From a physiological perspective, the flow of blood and water can be explained through the lens of medical science. When a person undergoes severe physical trauma, such as that experienced during crucifixion, the body can exhibit specific responses. Crucifixion was a brutal method of execution designed to maximize suffering. Jesus would have endured severe scourging, carrying the cross, and then being nailed to it. This would have resulted in significant blood loss, dehydration, and physical shock.

One plausible medical explanation is that Jesus suffered from hypovolemic shock, a condition caused by severe blood loss and dehydration, leading to heart failure. When the spear pierced His side, it likely punctured the pericardium, the sac surrounding the heart. The pericardium contains a small amount of fluid, and under the stress of crucifixion, it could have accumulated more fluid. Thus, the “water” could be pericardial fluid, while the “blood” would be from the heart or surrounding vessels. This explanation aligns with the observations of many medical experts who have studied the crucifixion in detail.

However, the physiological explanation, while informative, only scratches the surface of the event's significance. Theologically, the flow of blood and water from Jesus’ side carries profound symbolism that resonates deeply within Christian doctrine.

Firstly, the blood and water can be seen as symbols of the sacraments of the Eucharist and Baptism. The blood represents the Eucharist, where believers partake in the blood of Christ, symbolizing the new covenant and the forgiveness of sins. Jesus Himself, during the Last Supper, said, “This is my blood of the covenant, which is poured out for many for the forgiveness of sins” (Matthew 26:28). The water symbolizes Baptism, which signifies purification, rebirth, and the washing away of sins. In John 3:5, Jesus tells Nicodemus, “Truly, truly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God.”

The early Church Fathers also saw deep significance in this event. For instance, St. Augustine, in his work "Tractates on the Gospel of John," interpreted the blood and water as symbols of the Church. He wrote, “The Evangelist has expressed himself carefully. He does not say that he struck the side, or wounded the side, or anything else, but that he opened the side. Hence, the door of life was opened, from which the sacraments of the Church have flowed forth, without which there is no entrance to the life which is true life.”

Furthermore, the dual flow of blood and water can be seen as a fulfillment of Old Testament prophecy and typology. In Zechariah 12:10, it is written, “And I will pour out on the house of David and the inhabitants of Jerusalem a spirit of grace and pleas for mercy, so that, when they look on me, on him whom they have pierced, they shall mourn for him, as one mourns for an only child, and weep bitterly over him, as one weeps over a firstborn.” This prophecy is echoed in John 19:37, where John explicitly connects the piercing of Jesus to this verse in Zechariah.

Moreover, the flow of blood and water from Jesus’ side can be seen as a new creation narrative. Just as Eve was formed from the side of Adam, the Church—the Bride of Christ—is born from the side of Jesus. This imagery is powerful and speaks to the intimate relationship between Christ and His Church. Ephesians 5:25-27 illustrates this relationship: “Husbands, love your wives, as Christ loved the church and gave himself up for her, that he might sanctify her, having cleansed her by the washing of water with the word, so that he might present the church to himself in splendor, without spot or wrinkle or any such thing, that she might be holy and without blemish.”

Additionally, the blood and water signify the totality of Jesus’ sacrifice. Blood alone could symbolize death and suffering, but the addition of water suggests life and cleansing. It is a holistic representation of what Jesus accomplished on the cross—both the atonement for sin and the provision of new life. Hebrews 9:22 underscores the necessity of blood for the forgiveness of sins: “Indeed, under the law almost everything is purified with blood, and without the shedding of blood there is no forgiveness of sins.” The water, then, complements this by symbolizing the ongoing process of sanctification and renewal.

The apostle John, who recorded this event, emphasized its importance by noting his eyewitness testimony. In John 19:35, he writes, “He who saw it has borne witness—his testimony is true, and he knows that he is telling the truth—that you also may believe.” John’s insistence on the veracity of this detail suggests that he saw it as crucial for understanding the full scope of Jesus’ redemptive work.

In summary, the flow of blood and water from Jesus’ side when He was pierced by the Roman soldier is rich with meaning. Medically, it can be explained by the severe trauma and physical conditions associated with crucifixion. Theologically, it represents the sacraments of the Eucharist and Baptism, fulfills Old Testament prophecy, symbolizes the birth of the Church, and signifies the completeness of Jesus’ sacrifice. This event, recorded with such care by John, invites believers to delve deeper into the mystery of Christ’s passion and to appreciate the profound love and sacrifice that it represents.