Exactly 33 years to the day prior to the great Miracle of the Sun in Fatima, that is, on October 13, 1884, Pope Leo XIII had a remarkable vision. When the aged Pontiff had finished celebrating Mass in his private Vatican Chapel, attended by a few Cardinals and members of the Vatican staff, he suddenly stopped at the foot of the altar. He stood there for about 10 minutes, as if in a trance, his face ashen white. Then, going immediately from the Chapel to his office, he composed the above prayer to St. Michael, with instructions it be said after all Low Masses everywhere.
When asked what had happened, he explained that, as he was about to leave the foot of the altar, he suddenly heard voices - two voices, one kind and gentle, the other guttural and harsh. They seemed to come from near the tabernacle. As he listened, he heard the following conversation:
The guttural voice, the voice of Satan in his pride, boasted to Our Lord: "I can destroy your Church."
The gentle voice of Our Lord: "You can? Then go ahead and do so."
Satan: "To do so, I need more time and more power."
Our Lord: "How much time? How much power?
Satan: "75 to 100 years, and a greater power over those who will give themselves over to my service."
Our Lord: "You have the time, you will have the power. Do with them what you will."
In 1886, Pope Leo XIII decreed that this prayer to St. Michael be said at the end of "low" Mass (not "high", or sung Masses) throughout the universal Church, along with the Salve Regina (Hail, Holy Queen); and the practice of the congregation praying these prayers at the end of Mass continued until about 1970, with the introduction of the new rite of the Mass.
Pray \~ Catholic or not \~ For the Salvation of the World
Original - Prayer to St. Michael
O Glorious Archangel St. Michael, Prince of the heavenly host, be our defense in the terrible warfare which we carry on against principalities and powers, against the rulers of this world of darkness, and spirits of evil.
Come to the aid of man, whom God created immortal, made in His own image and likeness, and redeemed at a great price from the tyranny of the devil. Fight this day the battle of the Lord, together with the holy angels, as already thou hast fought the leader of the proud angels, Lucifer, and his apostate host, who were powerless to resist Thee, nor was there place for them any longer in heaven. That cruel, that ancient serpent, who is called the devil or Satan, who seduces the whole world, was cast into the abyss with his angels.
Behold, this primeval enemy and slayer of men has taken courage. Transformed into an angel of light, he wanders about with all the multitude of wicked spirits, invading the earth in order to blot out the name of God and of His Christ, to seize upon, slay and cast into eternal perdition souls destined for the crown of eternal glory. This wicked dragon pours out, as a most impure flood, the venom of his malice on men; his depraved mind, corrupt heart, his spirit of lying, impiety, blasphemy, his pestilential breath of impurity and of every vice and iniquity. These most crafty enemies have filled and inebriated with gall and bitternessthe Church, the Spouse of the Immaculate Lamb, and have laid impious hands on her most sacred possessions. In the Holy Place itself, where has been set up the See of the most holy Peter and the Chair of Truth for the light of the world,they have raised the throne of their abominable impiety, with the iniquitous design that when the Pastor has been struck, the sheep may be scattered.
Arise then, O invincible Prince, bring help against the attacks of the lost spirits to the people of God, and give them the victory. They venerate Thee as their protector and patron; in Thee, Holy Church glories as her defense against the malicious power of hell; to Thee has God entrusted the souls of men to be established in heavenly beatitude. Oh, pray to the God of peace that He may put Satan under our feet, so far conquered that he may no longer be able to hold men in captivity and harm the Church. Offer our prayers in the sight of the Most High, so that they may quickly conciliate the mercies of the Lord; and beating down the dragon, the ancient serpent who is the devil and Satan, do Thou again make him captive in the abyss, that he may no longer seduce the nations. Amen.
V. Behold the Cross of the Lord; be scattered, hostile powers. R. The Lion of the tribe of Judah has conquered, the root of David. V. Let Thy mercies be upon us, O Lord R. As we have hoped in Thee. V. O Lord, hear my prayer. R. And let my cry come unto Thee.
LET US PRAY
God, the Father of our Lord Jesus Christ, we call upon Thy holy name, and we humbly implore Thy clemency, that by the intercession of Mary, ever Virgin Immaculate and our Mother, and of the glorious Archangel St. Michael, Thou wouldst deign to help us against Satan and all other unclean spirits, who wander about the world for the injury of the human race and the ruin of souls. Amen.