The vision of Pope Leo XIII
The prayer to St. Michael
"Saint Michael, the Archangel, defend us in battle; be our protection against the wickedness and snares of the devil. May God rebuke him, we humbly pray, and do thou, O prince of the heavenly host, by the power of God, thrust into Hell, Satan and all the other evil spirits, who prowl throughout the world, seeking the ruin of souls. Amen."
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.
John Paul II and St. Michael
However, at the end of his Angelus message given in St. Peter’s Square, Sunday, April 24, 1994, Pope John Paul II urged Catholics to recite this prayer to Saint Michael once again:
"The prayer can fortify us for that spiritual battle about which the Letter to the Ephesians speaks [of]: "Finally, draw your strength from the Lord and from his mighty power."(Ephesians 6:10). And to this same battle that the Book of the Apocalypse refers [to], recalling in front of our eyes the image of St. Michael the Archangel (cf. Revelations 12:7). Surely, this scene was very present to Pope Leon XIII, when, at the end of the previous century, he introduced to the entire Church a special prayer to St. Michael: ‘St. Michael the Archangel, defend us in battle; be our protection against the wickedness and snares of the devil… ’
"Even if today this prayer is no longer recited at the end of the Eucharistic celebration, I invite all to not forget it, but to recite it in order to obtain help in the battle against the forces of darkness and the spirit of this world."