The main reason for devotion to the Sacred Heart is the love of Jesus for His Father, and thus for mankind. In the Scriptures, the heart is often employed as a symbol of God’s love for men and of their love for their Creator.
Indeed, the Old Testament enjoined believers:
“Thou shalt love the Lord thy God with thy whole heart, and with thy whole soul, and with thy whole strength. And these words which I command thee this day, shall be in thy heart” (Dt. 6:4-6). As a forerunning sign of the New Testament with its interior Law based on love, the Lord warned through the Prophet Jeremiah: “I will give my law in their bowels, and I will write it in their heart: and I will be their God, and they shall be my people” (Jer. 31:33-34). And through Ezekiel he announced: “And I will give you a new heart, and put a new spirit within you: and I will take away the stony heart out of your flesh, and will give you a heart of flesh” (Ez. 36:26). The prophet Zacharias foresaw that the Messiah would be killed and have his side pierced by a spear, and that a river of grace would pour upon men from His side: “And I will pour out upon the house of David, and upon the inhabitants of Jerusalem, the spirit of grace, and of prayers: and they shall look upon me, whom they have pierced: and they shall mourn for him as one mourneth for an only son, and they shall grieve over him, as the manner is to grieve for the death of the firstborn.” (Zac 12:9-10).
With the New Testament, these prophecies came true. When Jesus died on the cross and had his side pierced by the spear of the centurion, in the Temple of Jerusalem the veil preventing access to the Sancta Sanctorum was torn in two (Mt 27:51). This meant that the Redemption had been accomplished and thus the path to Divine grace was open so that the old Law with its rigor had now been replaced by the new Law based on love. Narrating the Passion of Christ, the Gospels say that in order to make sure that Jesus was actually dead, “one of the soldiers with a spear opened his side, and immediately there came out blood and water” (Jn 19:34). Saint John sees this event as the fulfilment of the prophecy of Zacharias: “these things were done, that the scripture might be fulfilled: You shall not break a bone of him…. and they shall look on him whom they pierced” (Jn 19: 36-37).
After His Resurrection, Jesus himself asked Thomas the doubtful to touch the wound in His side so that he would believe and take refuge in that Heart, now wide open to all those who do not refuse Divine Mercy (Jn 20:27-28).
The wound on the Redeemer’s side and His open and wounded Heart have been and will be objects of contemplation throughout the ages until the end of time. John Paul II teaches that “From the very beginning, the Church has contemplated the pierced heart of the crucified Christ from which came blood and water…in the heart of the Word Incarnate, the Fathers of the Christian East and West saw the beginning of the whole work of our salvation, the fruit of the love of the divine Redeemer.”
Indeed, we can say that “devotion to the Sacred Heart of Jesus is a devotional form of the prophetic and evangelic gaze of all Christians…on the side of Christ, transfixed by a lance.”
The devotion to the Sacred Heart has no other aim but to imitate the virtues of the Redeemer making His sentiments and desires, and especially His supernatural charity, one’s own. Jesus himself presented his Heart as an example to be imitated by all believers: “Take up my yoke upon you, and learn from me, because I am meek, and humble of heart: and you shall find rest for your souls” (Mt 11:28-29). Saint Paul exhorts the early Christians: “That Christ may dwell by faith in your hearts” (Eph 3:17) in order to attain the end of the commandment, which “is charity, from a pure heart, and a good conscience, and an unfeigned faith” (1 Tim 1:5).
The most beloved Apostle, St. John the Evangelist is considered to be the first devotee of the Sacred Heart and thus the patron of this devotion. In fact, during the Last Supper he had the holy audacity of leaning his head upon the Redeemer’s bosom, thus becoming the first to listen to the pulses of the Divine Heart (Jn 13:23). His gesture of reclining upon Jesus’ breast expressed the endless confidence, filial abandonment and familiarity the virgin Apostle felt for Him. St. John was trying to console Him by showing love and support. Through that gesture, Saint John received a torrent of grace that turned him into the “eagle” of the Apostolic College, who communicated to us the highest truths about the Word Incarnate. Furthermore, he had the privilege of representing the nascent Church at the foot of the Cross and of receiving from Jesus Himself the role of protector of the Virgin Mary (Jn 19:26-27).