Edited and summarized from this original post: https://www.catholic.com/audio/caf/the-sacred-heart
The devotion has its origin in the Gospels, not explicitly, in John 19. One of the soldiers pierces our Lord’s side with a lance, and there flowed blood and water. St. John says that the one who is testifying knows his witness is true because he saw it happen. They regarded this as a miraculous event that blood and water would flow from a dead body.
As we know, blood doesn’t flow from a dead body as though the body were still pumping the blood. The blood is pulsing out of his body to indicate that there’s more there than just a representation of the dead Christ, but actually the living power of the divine Christ whose divine person is united to his precious blood.
It begins there because there always has been in the Church a devotion not explicitly to the heart of Christ, but to the mystery of that wound in his side. The saints have venerated that and contemplated that to the extent that through the wound is his heart. That’s why blood and water flowed forth. The blood and water symbolize the sacramental life of the church, so it’s the inception of the sacraments in their full sense. Christ completes his work on the cross and the sacraments receive their full potency, their full power flowing from his wounded heart which was pierced by the lance.
The awareness that sacramental life came from the wounded side of Christ in his perfected work on the cross was quite active and evident from the writings of St. Ephrem the Syrian, the 4th-century deacon, and what we would call now the Chaldean or the Syrian Church. Then the writings of the Fathers, St. Ambrose, St. Augustine, St. John Chrysostom; they all talk about that act of the wounding of our Lord’s side in significance for us spiritually.
It really takes off in the 13th century in Europe with the Benedictine nuns. The cloistered nuns, who were practically all Benedictines at that time, or Cistercians who follow the real Benedict, like the great St. Gertrude and St. Mechtilde. They had a personal intense devotion to the heart of Christ, specifically the heart of Christ, but always related to that wound in his side. They wrote about it and meditated on it and wrote poetry for it.
A great Norbetine of our own order, the order I (Father Hugh Barbour) belong to, wrote also in the 13th century, St. Herman Joseph who was in the Rhineland of Germany, and wrote what is the first known hymn in honor of the Sacred Heart.
St. John Eudes, who founded the Eudist Fathers, promoted very vigorously an explicit devotion to the heart of Jesus. Of course, gloriously risen, having suffered his passion, still beating with love for us as an object of our veneration and devotion. He even wrote a Mass in office in honor of the Sacred Heart, because back then in France in the 17th century, they were kind of easy-going about writing new liturgical texts. That might surprise some people, but they did that back then. He promoted devotion to the Sacred Heart of Jesus and of the heart of Mary. It was the two hearts.
Now, where did this come from? It came from a meditation a little different from the Middle Ages where they’re actually considering the passion in and of itself. It came from a more modern, in the broad sense of modern–like post-Descartes modern, 17th century on–a sense of wanting to participate in the inner states of the life of Christ of the word made flesh. What is he thinking? What is he feeling? What are the thoughts of his heart? What are his experiences? What are the secrets hidden in his inner life? That’s a very modern way to approach it.
St. Louis de Montfort’s consecration to Mary is a consecration to Jesus, the incarnate word at the hands of Mary. That is this great focus on the inner life of the incarnate word and the inner life of Mary. So there’s a devotion, for example, of her heart. That’s where the heart’s mentioned in the Scriptures quite explicitly, with Mary, that she ponders these things in her heart. In the Scriptures, we don’t hear a reference to our Lord’s heart directly, but we hear the event of the piercing of his heart. That particular spirituality had a tremendous impact and the attractiveness of this devotion to the inner life, the thoughts of the hearts of Jesus and Mary. Their love for us and their feelings for us really had great popular appeal.
Our Lord Jesus Christ himself came to ratify this movement of the Holy Spirit among his people in his revelations to St. Margaret Mary, a nun of the Visitation (the order founded by St. Frances de Sales), to whom He appeared revealing his desire that devotion to his Sacred Heart be established throughout the world and that a feast day be given to the Sacred Heart and various promises associated with devotion of the Sacred Heart, and in particular, a Mass in devotion in reparation for the outrages by which He’s offended by neglect of the blessed sacrament by clergy, by neglect of the sacrament altogether by Christians who don’t receive the Holy Eucharist, for those who receive the Holy Eucharist unworthily, for the lack of physical external reverence offered, blasphemies uttered against the doctrine itself by heretics, etc.
Our Lord appears to St. Margaret Mary and he says, “Behold this heart which so loved men and in return receives only indifference or contempt.” Well if you lived a life where most people regarded you at best with indifference or even contempt, you could imagine what a man or woman of sorrow you would be. Our Lord presents himself in this vein. He asks for this devotion to repair and she courageously, through her spiritual rector, St. Claude de la Colombiere, the Jesuit Father, began to promote the devotion. Little by little, it grew and grew with lots of opposition, but finally, it was recognized by the Popes of Rome.
The Visitation Sisters got a Mass in office and then it was extended ultimately to the whole church on a lower level by Gregory XVI, and then later on by Pius IX, and so on into the 20th century when, as a supreme act of magisterium regarding the Sacred Heart, Pope Pius XII had an encyclical of the Sacred Heart which gives the most perfect presentation of the doctrine. Pope John Paul II in his encyclical on mercy gives an outline of the devotion of the Sacred Heart too which is different in tone from Pius XII, but certainly not a different doctrine.
It’s a doctrine that developed over a long period of time but with great success among the faithful. If you went to Ireland at a certain age, there wouldn’t be a single household without a picture of the Sacred Heart. It was one of the things that was promoted, to enthrone the image of the Sacred Heart in the house as king of one’s family. That’s one of the most beautiful devotions. Do it in your own house.
When we adore our Lord, we’re thinking of his heart, we’re thinking of his face, his eyes. Basically, we’re thinking of his intellect and his will, but shown forth in a body. A heart expresses both thoughts and a disposition of will so that he both knows us and loves us with his heart. Not only with his mind, but he looks upon us with his eyes and his face so that we will receive consolation and confidence to approach him.
In a certain true sense, we do adore his Sacred Heart in so far as it is the representation of his person, his divine person, and his human nature, but the Church is sensitive enough to this issue that, something little known, she forbade that there should be in churches a veneration just of an image of the heart without the whole body being there or at least from the waist up. That is for an altar to the Sacred Heart, you need a statue or a painting of our Lord there with his head and his hands and his arms. When he appeared to St. Margaret Mary, he didn’t just appear as a disembodied heart, he appeared as a man holding forth his heart. Now, it was all the way out of his body to show how much he wanted to give it to us, but still, all there to be interpreted.
We can use the Sacred Heart as a symbol as, say, a decoration on a pious prayer book or whatnot, but we don’t in a church. If we’re going to dedicate a church to the Sacred Heart, we don’t put up a giant heart man and venerate it, but if we have an image of our Lord showing his heart, we venerate that. We venerate all of that, but the point is that the church’s guidance regarding iconography is that Jesus has to be represented along with his heart, not simply the heart by itself unless it’s simply a decoration. A vestment with a Sacred Heart on it is no problem, but an altar to the Sacred Heart needs a statue or a painting of him.