This devotion to the Sacred Heart was given in a private revelation by Our Lord to St. Margaret Mary Alacoque. The objective of this devotion is honoring His Sacred Heart of Our Lord with an ardent love, and to make reparation for the outrages offered to Him in the past, as well as for those which he daily receives in the Blessed Eucharist. The Lord has promised to St. Margaret Mary twelve beautiful gifts of grace to those who attend at least 9 consecutive First Fridays, with the customary practices of confession within a forthnight (7 days before or 7 days after) and Holy Communion on the First Friday of each month.
The greatest grace the Lord deigned to promise to His little ones is the grace of final penitence. This may sound surprising, but is perfectly in accordance with the belief of the Church that “final perseverance is a gratuitous gift of God’s goodness, and cannot be merited as an acquired right by any individual act of ours” (words from the Council of Trent, Session 6 Chapter 13, the opposite being condemned as a grave error in Canon 22).
This devotion was acknowledged by the Church. In 1765 Pope Clement XIII approved the Mass and Office in honor of the Sacred Heart of Jesus, and Pope Pius IX extended the feast to the universal Church. Furthermore, Pope Pius XI, in order that, by its solemnity, the feast might answer more fully to the greatly widespread devotion of the Christian people, raised the feast of the most Sacred Heart of Jesus to the rite of a double of the first class (which corresponds to today’s ranking of Solemnity), with an octave (which is now a Privileged Octaves of the Third Order, along with Christmas and the Ascension); and moreover, that the violated rights of Christ, the supreme King and most loving Lord, might be repaired, and that the sins of the nations might be bewailed, he ordered that annually, on that same feast-day, there should be recited an expiatory form of prayer in all the churches of the Christian world.
Furthermore, the Roman Raccolta included the First Friday devotion as part of the prayers endowed with indulgences (with the addition of the customary prayers for the intentions of the Holy Father), including the assistance at the public exercises in honor of the Sacred Heart [or] the private recitation of some prayers in reparation for the injuries against the Sacred Heart. The Holy See went even further, and blessed with indulgences the faithful who would recite devout prayers of reparation on other Fridays of the year.
There are also many beautiful Encyclical Letters on the Sacred Heart.
Leo XIII, for instance, would write that “There is in the Sacred Heart the symbol and express image of the infinite love of Jesus Christ which moves us to love in return”.
Pius XII would write: ".the Heart of the Incarnate Word is deservedly and rightly considered the chief sign and symbol of that threefold love with which the divine Redeemer unceasingly loves His eternal Father and all mankind…Since Sacred Scripture and the official teaching of the Catholic faith instruct us that all things find their complete harmony and order in the most holy soul of Jesus Christ, and that He has manifestly directed His threefold love for the securing of our redemption, it unquestionably follows that we can contemplate and honor the Heart of the divine Redeemer as a symbolic image of His love and a witness of our redemption and, at the same time, as a sort of mystical ladder by which we mount to the embrace of “God our Savior.”
May the Lord bless you for your loving kindness towards His most Sacred Heart. You do not need to let the priest know that you are confessing for that reason (of course, you confess because you seek forgiveness of sins and reconciliation with God) but if you are not conscious of grave sins (God bless your soul) you may let the priest know that you wish to be properly disposed for the Communion of Reparation to the Sacred Heart (or something around that concept).
