The Penitential Rite
After the greeting, comes the Penitential Rite. The Rite is introduced by the priest with the words,
Brethren [brothers and sisters], let us acknowledge our sins, and so prepare ourselves to celebrate the sacred mysteries.
We often wash our hands or use sanitizer before beginning a task like cooking or when finishing a task like gardening. It marks an end of one thing and a start of another. We can think of the Penitential Rite as a way of cleansing to mark our movement from the work of our lives into the work of God.
It must be remembered that the Penitential Rite is not the same as going to confession. If one is aware of serious/mortal sin, one should be going to the Sacrament of Reconciliation as soon as possible; if at all possible before attending Mass the next Sunday. Serious sins are to be confessed in number and kind (i.e., what exact action did you do and how many times did you do it.)
As for venial sins, they can be forgiven in other ways. St. Thomas Aquinas gives an interesting list:
[T]here are many remedies against venial sins; for example, beating of the breast, sprinkling with holy water, extreme unction, and every sacramental anointing; a bishop’s blessing, blessed bread, general confession, compassion, the forgiveness of another’s faults, the Eucharist, the Lord’s Prayer, and other sorts of light penance.
But back on point, the Penitential Rite reminds us that we may all come from different places, professions, forms of families; we may gather as male and female; young and old; clergy and laity; but what we all have in common with 99.99+ of humanity (actually 100% minus 2, Jesus and the Blessed Virgin Mary being the exceptions ) is that we are sinners. We are all in need of God’s mercy, particularly as we approach so great a thing as the Mass.
There is then, appropriately, a moment of silence that allows us to do what is asked, viz., to call to mind our sins and acknowledge them. When we do that, we are even more aware of God’s great work in giving us His mercy.
