When Jesus was pierced, why did blood and water come out of His side?

from the old testament

• While this question is answered in the New Testament, the Old Testament provides some background in anticipation of Jesus’ death.
• The first instance is in the Passover story. In that historical account, on the night before the Israelites were freed from slavery, God came to kill the first-born of everyone in Egypt. However, He provided a way for the Israelites to escape by telling them to kill a perfect lamb, saying “you shall not break any of its bones” (Exodus 12:46). The blood of that lamb was to be placed on the doorposts so that God would pass over those houses. John would connect this to when Jesus died.
• In addition to Passover, there was also an Old Testament promise that the Messiah would be pierced. God said, “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” (Zechariah 12:10). John also connects Jesus’ death to this prophecy.

from the new testament

• John provided a unique eyewitness account of the end of the crucifixion. He wrote, “But one of the soldiers pierced his side with a spear, and at once there came out blood and water” (John 19:34). He added that “he who saw it has borne witness,” emphasizing that John personally witnessed the event (John 19:35).
• The context helps explain why the soldier did this. Because of the approaching Sabbath, the authorities requested that the victims’ legs be broken to speed death. However, “when they came to Jesus and saw that he was already dead, they did not break his legs” (John 19:31–33). Instead, they thrust a spear into His side to confirm His death (John 19:34).
• Based on what is known about crucifixion, death usually occurred due to hypovolemic shock from blood loss or asphyxiation as the victim lost the strength to lift themselves to breathe. Both conditions can cause fluid to build up in the chest, either in the sac surrounding the heart (pericardial effusion) or around the lungs (pleural effusion).
• A spear pushed under the ribs could enter the chest cavity and rupture these fluid-filled spaces along with blood vessels, releasing a clear, watery fluid along with blood. John’s simple description aligns with what one would expect from this type of death and shows that Jesus was truly dead.
• However, John also realized that there was more to this than simply confirming Jesus' death. Instead, the way Jesus died confirmed that He was the one Scripture had prophesied. He said, “These things took place that the Scripture might be fulfilled: ‘Not one of his bones will be broken.’ And again another Scripture says, ‘They will look on him whom they have pierced’” (John 19:36–37). Jesus’ unbroken bones identified Him as the true Passover Lamb (Exodus 12:46), and being pierced connected His suffering to the promised figure who would be seen and mourned (Zechariah 12:10).

implications for today

Jesus’ death was a real event, witnessed and described by John, one of His closest followers. The reason He died is significant: all sin requires death (Romans 6:23a). Because of this, Jesus couldn’t just suffer—He had to die. His sacrifice was necessary to pay the price for our sin.

But incredibly, Jesus didn’t stay dead. Three days later, He rose again—conquering death itself—and is now alive in heaven. His resurrection is proof that His death completely satisfied the punishment for sin. It shows that His sacrifice was enough to bring us forgiveness and new life.

Because of what Jesus did, He made a way for you to be saved. If you turn from your sins and trust in what Jesus has already done, God promises to consider Jesus’s death as the payment for your sins. There’s no reason to carry the burden of guilt alone—Jesus has paid it all.

So, we implore you today: receive this gift of salvation! Come to Jesus with an open heart and trust in Him. He’s ready to give you a new, eternal life.