Fountain of Mercy: How the Early Fathers and Later Mystics Exposed the Heart of Christ

Scholars tell us that devotion to the Sacred Heart of Jesus began in the Middle Ages, but rich theological reflection on the heart of Jesus goes all the way back to St. John the Evangelist at the crucifixion and the early Church Fathers. It was the mystics who built on that foundation.

It was the "beloved disciple," John, whose head rested on the heart of Jesus as depicted in many Last Supper paintings. John recorded that the disciple whom Jesus loved "was reclining next to him" (Jn 13:23) and was the eyewitness to the piercing of Jesus’ heart by the Roman soldier’s lance. Later, the early Church Father Origen (c. 184–253 AD) commented on this moment, noting that by resting his head on Jesus' chest, John was able to draw deep, hidden spiritual secrets directly from the internal reservoir of Christ’s heart.

John gave a detailed account of this deeply theological moment in his Gospel…

But when they came to Jesus and saw that he was already dead, they did not break his legs, but one soldier thrust his lance into his side, and immediately blood and water flowed out. An eyewitness has testified, and his testimony is true; he knows* that he is speaking the truth, so that you also may [come to] believe (John 19:33-35).

When researching the writings of St. Polycarp, the church father who studied under the Apostle John, I expected to find meaningful commentary about the pierced side of Christ. Instead, I found something much better. His martyrdom story centers around the heart of Jesus. When authorities attempted to burn Polycarp at the stake in the stadium, the flames miraculously failed to consume his body. To finish the execution, a guard was ordered to stab him with a dagger. Upon being pierced, a miraculous outpouring of blood flowed so heavily from his heart that it extinguished the surrounding fire. Like John’s Master, Jesus on the cross, John’s disciple, Polycarp, suffered the same fate: a pierced heart.

Overall the fathers of the Church viewed the pierced heart and wounded side of Jesus as the gateway to divine life, the birth place of the Church, a fountain of sacramental grace, the door of life, and spiritual wellspring of the Holy Spirit. 

Jesus’ Heart as the Source of the Sacraments

The Church Fathers almost universally interpreted the blood and water flowing from Christ’s side as the raw source of the Christian sacraments. The Water which cleanses in Baptism and the Blood which fills the chalice of the Eucharist are like the rib taken from Adam to fashion Eve. Like Eve, the spouse of Adam, the Church is built up from the water and blood side of the New Adam. 

Without water and blood the human body would be depleted as 75% of the body is water alone. For a 150lb man, approximately 11.2 lbs is blood alone. It’s easy to see why the early church Fathers, who were pre-science, considered blood and water as the ‘life’ of a person being poured out. The theological analogy of Baptism (water) and Eucharist (blood) as that from which the Body of Christ the Church is built is perfect.

It was Tertullian (155–220 AD) who referred to the blood and water as the "two baptisms" flowing from a single wound to cleanse and choose believers. St. Augustine (354–430 AD): Famously noted that the John’s gospel used the word "opened side” rather than "wounded" to show that the door of life was thrown wide open, pouring out the sacraments without which no one can enter true life. 

Jesus’ Heart Gave Birth to the Church (The New Eve)

The Patristic writers drew a direct typological parallel between the Book of Genesis and the Crucifixion.  Just as God cast a deep sleep over Adam and built Eve from his side, Christ went into the sleep of death so His Bride, the Church, could be formed from His pierced side. St. John Chrysostom (347–407 AD): Explicitly preached that "Christ fashioned the Church from his side," comparing the blood and water to a mother who nourishes her newborn child with her own body. Around the same time in church history images of a pelican pecking at her own bloody flesh to feed her young started to emerge. 

St. Irenaeus (130–202 AD): Described the Church as drawing from the "fountain of living water that flows for us from the Heart of Christ," equating the Spirit with this lifespring. 

Jesus’ Heart Exposed to The Mystics

Two saints, perhaps more than anyone else, have built upon the patristic foundation of the theology of the pierced heart of Jesus through their own mystical and personal revelations. 

St. Margaret Mary Alocoque, a French Visitation nun and mystic (1647-1690) popularized the devotion to the Sacred Heart of Jesus, emphasizing His love and the reparation for human ingratitude. 

St. Faustina Kolwalska was a Polish Catholic religious sister and mystic (1905-1938). Her revelations of the Divine Mercy—originating from the same wounded heart—are often seen as the culmination and completion of St. Margret Mary’s message, emphasizing the ocean of mercy gushing forth from a fountain (the heart of Jesus). 

St. Faustina Kowalska’s famous Diary, Divine Mercy in My Soul, contains more than 200 references to the Merciful and Sacred Heart of Jesus, highlighting it as the ultimate fountain of love, refuge, and grace. In her diary, Jesus described the wound in his heart as the "fountain of unfathomable mercy," pouring out graces for souls (Diary, 1190, 1182, 1777, 1796). 

We are all familiar with St. Faustina’s  Divine Mercy image of two rays of light streaming from the wounded side of Christ, one blue and one red with the words below, “Jesus, I trust in you”. According to St. Faustina, Jesus said about that image, “I am offering people a vessel with which they are to keep coming for graces to the fountain of mercy. That vessel is this image with the signature: “Jesus, I trust in You” (Diary, 327).  

My Heart overflows with great mercy for souls, and especially for poor sinners … it is for them that the Blood and Water flowed from my Heart as from a fount overflowing with mercy (Diary, 367).  

Jesus’ Heart Exposed in the Monstrance

St. Cyprian (c. 210–258 AD) was one of the first to draw a parallel between the water and blood from the heart of Jesus and the mixing of water (humanity) and wine (divinity) in the Eucharistic chalice. He pointed out that the blending of the water and wine before the consecration is meant to show the permanent, inseparable union between Christ’s heart and humanity. 

Recent scientific studies of the various eucharistic miracles have shed more light on the heart of Jesus and the consecrated, eucharistic Host. Scientists have found that the blood is always AB. This is significant because this is the universal blood type. Like the blood of Christ, it is shed for all people, for all times as an ocean of mercy. Furthermore, the tissue has been revealed as human heart tissue from the left ventricle.* The left ventricle is the side of the heart that pumps the blood out as a fountain of mercy.

Both Saint Margaret Mary Alocoque and Saint Faustina Kowalska had a devotion to Eucharistic adoration. They sensed mystically, what we all know through these scientific studies, that just under the appearances of bread and wine, the Eucharist is the primarily pulsating heart of Christ. Consider these quotes on Eucharistic Adoration by these two lovers of the Sacred Heart…

Saint Margaret Mary:

• "My greatest happiness is to be before the Blessed Sacrament, where my heart is, as it were, in Its center."
• "When we pray before the Blessed Sacrament, we should often take time to think about how much Jesus loves us and suffered for us. Jesus’ holy passion and death should fill us with joy and wisdom to help us love as He did."

Saint Faustina:

• "When the priest exposed the Blessed Sacrament, and the choir began to sing, the rays from the (Divine Mercy) image pierced the Sacred Host and spread out all over the world.  Then I heard these words: 'These rays of mercy will pass through you, just as they have passed through this Host, and they will go out through all the world.'  At these words, profound joy invaded my soul." -St. Faustina
• "My Heart overflows with great mercy for souls and especially for poor sinners…. I desire to bestow my graces upon souls (from the tabernacle) but they do not want to accept them. You, at least, come to Me as often as you can and take these graces they do not want to accept. In this way you will console my Heart." -Jesus to St. Faustina

*Eucharistic Miracle of Buenos Aires (Argentina, 1996): When pieces of the host were placed in water to dissolve, they turned into a red substance. Pathological testing by Dr. Frederic Zugibe, a prominent forensic pathologist at Columbia University, concluded it was human heart muscle from the left ventricle wall. The tissue was also heavily infiltrated with white blood cells, indicating it was from a living, beating heart under severe stress.

Miracle of Lanciano (Italy, 8th Century): During independent scientific testing in the 1970s and 1980s by the World Health Organization and other experts, analysis revealed that the flesh was heart muscle and specifically identified tissue from the left ventricle.