A beautiful prayer! You’re referencing the famous prayer to Saint Michael, often recited for protection and defense. The full prayer goes like this:
“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 evil spirits
who prowl throughout the world seeking the ruin of souls.
Amen.”
This prayer, traditionally attributed to Pope Leo XIII, calls upon Saint Michael’s intercession to safeguard believers from evil and harm.