According to the Gospel of John (John 19:31-37), a Roman soldier pierced Jesus' side with a spear while he was on the cross. This was done to ensure that he was dead. Here's why:
* To ensure death: Roman practice was to break the legs of those being crucified to hasten their death (crurifragium). This prevented them from pushing themselves up to breathe. However, when the soldiers came to Jesus, they saw that he was already dead, so they did not break his legs.
* Fulfillment of prophecy: The Gospel of John states that this action fulfilled two Old Testament prophecies: "Not one of his bones will be broken" (Psalm 34:20) and "They will look on the one they have pierced" (Zechariah 12:10). The piercing was seen as a way to confirm Jesus as the Messiah and to demonstrate the fulfillment of scripture.
* Symbolic significance: The blood and water that flowed from the wound are seen as having symbolic importance. They are interpreted as representing the sacraments of baptism and the Eucharist, signifying cleansing and new life, respectively.
The soldier who pierced Jesus is traditionally known as Longinus, and he is venerated as a saint in some Christian traditions.