St. John the Apostle highlights the Sacred Heart of Christ in his gospel when he relates that he rested his head on the chest of Jesus, after our Savior shared the heartbreaking news of Judas’s betrayal (John 13:23).
A few chapters later, from the foot of the Cross, John recollects a crucial detail:
But one of the soldiers pierced his side with a spear, and at once there came out blood and water (John 19:34, emphasis mine).
St. John’s description of these powerful details draws us into a spiritual and physical reality: The moment when Jesus’s heart was pierced for our salvation, and blood and water flowed forth, fulfilled the prophecy in Zechariah 12:10, giving us indisputable proof of the fulfillment of God’s plan. St. John wants us to pay attention to these details and come to believe that Jesus, the King of Kings, died on a cross for us. And that as he did so, blood and water flowed from his side.
The Church teaches that this blood and water represented Eucharist and Baptism, respectively (CCC 1225). Water cleanses, and blood represents new life in Christ. These two features encapsulate the significance of this scripture passage and point to why the heart of Christ is so essential for us: Out of his pierced heart flowed his very life into his eternal Body, the Church.
In “The Blood and Water from His Side,” from his Catechesis, St. John Chrysostom writes this about John 19,
As God took a rib from Adam’s side to fashion a woman, so Christ has given us blood and water from his side to fashion the Church. God took a rib when Adam was in a deep sleep, and in the same way Christ gave us the blood and water after his own death.
Sacred Heart of Jesus, draw me to your side, that I might abide forever there.