The legend behind this Catholic prayer has it that Pope Leo XIII, was going about his duties as Pope when suddenly, he fell to the floor. Doctors were immediately called to his side but they believed him to be dead because he showed no signs of life. Shortly, Pope Leo XIII awoke and cried out, "Oh what a horrible picture I was permitted to see!" He then told everyone that he saw all the future struggles of the Catholic Church and the legion of forces that would attack it. Then he saw the Archangel Michael, triumph over Satan and then cast Satan and his minions back into hell. As a result of this vision he composed this prayer.
The English version of the prayer:
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 Divine Power of God -
cast into Hell, Satan and all the evil spirits,
who roam throughout the world seeking the ruin of souls.
The Latin version of the prayer:
Sancte Michael Archangele
Sancte Michael Archangele,
defende nos in proelio;
contra nequitiam et insidias diaboli esto praesidium.
Imperat illi Deus; supplices deprecamur:
tuque, Princeps militiae coelestis,
Satanam aliosque spiritus malignos,
qui ad perditionem animarum pervagantur in mundo,
divina virtute in infernum detrude.
A longer version of this prayer is used in the Rite of Exorcism.
'"May prayer strengthen us for the spiritual battle we are told about in the Letter to the Ephesians: 'Draw strength from the Lord and from His mighty power' (Ephesians 6:10). The Book of Revelation refers to this same battle, recalling before our eyes the image of St. Michael the Archangel (Revelation 12:7). Pope Leo XIII certainly had a very vivid recollection of this scene when, at the end of the last century, he introduced a special prayer to St. Michael throughout the Church. Although this prayer is no longer recited at the end of Mass, I ask everyone not to forget it and to recite it to obtain help in the battle against forces of darkness and against the spirit of this world." -Pope John Paul II