21 There is surely no reason for doubting, Venerable Brethren, that from this devotion piously established and commanded to the whole Church, many excellent benefits will flow forth not only to individual men but also to society, sacred, civil, and domestic, seeing that our Redeemer Himself promised to Margaret Mary that "all those who rendered this honor to His Heart would be endowed with an abundance of heavenly graces." Sinners indeed, looking on Him whom they pierced ( John xix, 37), moved by the sighs and tears of the whole Church, by grieving for the injuries offered to the supreme King, will return to the heart ( Isaias xlvi, 8), lest perchance being hardened in their faults, when they see Him whom they pierced "coming in the clouds of heaven" ( Matth. xxvi, 64), too late and in vain they shall bewail themselves because of Him (Cf. Apoc . i, 7). But the just shall be justified and shall be sanctified still (Cf. Apoc . xxii. 11) and they will devote themselves wholly and with new ardor to the service of their King, when they see Him contemned and attacked and assailed with so many and such great insults, but more than all will they burn with zeal for the eternal salvation of souls when they have pondered on the complaint of the Divine Victim: "What profit is there in my blood?" ( Psalm xxix, 10), and likewise on the joy that will be felt by the same Most Sacred Heart of Jesus "upon one sinner doing penance" ( Luke xv, 10). And this indeed we more especially and vehemently desire and confidently expect, that the just and merciful God who would have spared Sodom for the sake of ten just men, will much more be ready to spare the whole race of men, when He is moved by the humble petitions and happily appeased by the prayers of the community of the faithful praying together in union with Christ their Mediator and Head, in the name of all. And now lastly may the most benign Virgin Mother of God smile on this purpose and on these desires of ours; for since she brought forth for us Jesus our Redeemer, and nourished Him, and offered Him as a victim by the Cross, by her mystic union with Christ and His very special grace she likewise became and is piously called a reparatress. Trusting in her intercession with Christ, who whereas He is the "one mediator of God and men" (1 Timothy ii, 5), chose to make His Mother the advocate of sinners, and the minister and mediatress of grace, as an earnest of heavenly gifts and as a token of Our paternal affection we most lovingly impart the Apostolic Blessing to you, Venerable Brethren, and to all the flock committed to your care. Given at Rome, at St. Peter's, on the eighth day of May, 1928, in the seventh year of Our Pontificate. Prayer of Reparation O sweetest Jesus, whose overflowing charity towards men is most ungratefully repaid by such great forgetfulness, neglect and contempt, see, prostrate before Thy altars, we strive by special honor to make amends for the wicked coldness of men and the contumely with which Thy most loving Heart is everywhere treated. At the same time, mindful of the fact that we too have sometimes not been free from unworthiness, and moved therefore with most vehement sorrow, in the first place we implore Thy mercy on us, being prepared by voluntary expiation to make amends for the sins we have ourselves committed, and also for the sins of those who wander far from the way of salvation, whether because, being obstinate in their unbelief, they refuse to follow Thee as their shepherd and leader, or because, spurning the promises of their Baptism, they have cast off the most sweet yoke of Thy law. We now endeavor to expiate all these lamentable crimes together, and it is also our purpose to make amends for each one of them severally: for the want of modesty in life and dress, for impurities, for so many snares set for the minds of the innocent, for the violation of feast days, for the horrid blasphemies against Thee and Thy saints, for the insults offered to Thy Vicar and to the priestly order, for the neglect of the Sacrament of Divine love or its profanation by horrible sacrileges, and lastly for the public sins of nations which resist the rights and the teaching authority of the Church which Thou hast instituted. Would that we could wash away these crimes with our own blood! And now, to make amends for the outrage offered to the Divine honor, we offer to Thee the same satisfaction which Thou didst once offer to Thy Father on the Cross and which Thou dost continually renew on our altars, we offer this conjoined with the expiations of the Virgin Mother and of all the Saints, and of all pious Christians, promising from our heart that so far as in us lies, with the help of Thy grace, we will make amends for our own past sins, and for the sins of others, and for the neglect of Thy boundless love, by firm faith, by a pure way of life, and by a perfect observance of the Gospel law, especially that of charity; we will also strive with all our strength to prevent injuries being offered to Thee, and gather as many as we can to become Thy followers. Receive, we beseech Thee, O most benign Jesus, by the intercession of the Blessed Virgin Mary, the Reparatress, the voluntary homage of this expiation, and vouchsafe, by that great gift of final perseverance, to keep us most faithful until death in our duty and in Thy service, so that at length we may all come to that fatherland, where Thou with the Father and the Holy Ghost livest and reignest God for ever and ever. Amen.
Source: Miserentissimus Redemptor (Vatican.va)