On the seventh day of Christmas my true love gave to me: seven swans a-swimming.
This is one of the biggest numbers that one can find in the Catholic Faith; 7 sacraments, 7 Corporal works of Mercy, 7 Spiritual works of Mercy, 7 Gifts of the Holy Ghost, 7 Angels who stand before the Lord, the 7 Sorrows and 7 Joys of both Our Lady and St. Joseph, and the 7 last words of Jesus. This is another of the numbers that represent completion and holiness for a week consists of seven days. There are plenty of sevens to be found elsewhere in the world and as such it also considered to be the luckiest number of all.
St. 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, cast into hell Satan and all his evil spirits, who prowl about the world, seeking the ruin of souls. Amen.