Exod 19:10

“However, even the people had to be purified two or three days beforehand, so as to come clean to the sacrifice, as we read in the Old Testament. They even used to wash their clothes. If such regard was paid in what was only the figure, how much ought it to be shown in the reality! Learn then, priest and Levite, what it means to wash your clothes. You must have a pure body wherewith to offer up the sacraments. If the people were forbidden to approach their victim unless they washed their clothes, do you, while foul in heart and body, dare to make supplication for others? Do you dare to make an offering for them?”