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.
Source: Miserentissimus Redemptor (Vatican.va)