The Catholic Defender: The Devotion to the Sacred Heart

The devotion began in the 1670s, when Jesus appeared multiple times to St. Margaret Mary Alacoque, a Visitation nun in France. Through these visions, He told her how He wished to be honored with the symbol of His heart, asking for the faithful to make amends for any wrongdoing they had done, frequently take Communion, and observe the Holy Hour. In 1856, the devotion was added to the church calendar by Pope Pius IX.

Pope Pius XII explained that the devotion to the Sacred Heart is connected to our worship of Christ as God incarnate:

It is altogether impossible to enumerate the heavenly gifts which devotion to the Sacred Heart of Jesus has poured out on the souls of the faithful, purifying them, offering them heavenly strength, rousing them to the attainment of all virtues. Therefore, recalling those wise words of the Apostle St. James, “Every best gift and every perfect gift is from above, coming down from the Father of Lights… That all may understand more exactly the teachings which the selected texts of the Old and New Testament furnish concerning this devotion, they must clearly understand the reasons why the Church gives the highest form of worship to the Heart of the divine Redeemer…The first, which applies also to the other sacred members of the Body of Jesus Christ, rests on that principle whereby we recognize that His Heart, the noblest part of human nature, is hypostatically united to the Person of the divine Word. Consequently, there must be paid to it that worship of adoration with which the Church honors the Person of the Incarnate Son of God Himself. We are dealing here with an article of faith, for it has been solemnly defined in the general Council of Ephesus and the second Council of Constantinople. Christ shown in stained glass in the Great Upper Church Secondly, Pope Pius XII shared how the devotion is related to Christ’s love for the human race: The other reason…arises from the fact that His Heart, more than all the other members of His body, is the natural sign and symbol of His boundless love for the human race. “There is in the Sacred Heart,” as Our predecessor of immortal memory, Leo XIII, pointed out, “the symbol and express image of the infinite love of Jesus Christ which moves us to love in return.” Significance of the Devotion Jesus’s profound love for us is demonstrated through His willingness to sacrifice His life for our sake. The love from His heart motivated all His actions — His inner life manifested in His demonstrated virtues and sacrifice. Yet this great love is often received with ingratitude, even by the faithful. The purpose of devotion to the Sacred Heart of Jesus is to focus our hearts on receiving and returning His love with gratitude — with all of our heart, soul, and strength — that He may be glorified. As Revelation 1:5-6 says, From Jesus Christ, the faithful witness, the firstborn of the dead and ruler of the kings of the earth. To him who loves us and has freed us from our sins by his blood, who has made us into a kingdom, priests for his God and Father, to him be glory and power forever [and ever]. Amen.

From https://www.nationalshrine.org/blog/what-is-the-devotion-to-the-sacred-heart-of-jesus/