Traditionally, we have placed fonts of holy water near the entrances of our churches. This placement and usage corresponds actually to Old Testament Jewish practices of purification: The Book of Leviticus prescribed various ritual purifications using water to remove the "uncleanness" associated, for instance, with coming into contact with a dead body, menstruation, childbirth, or leprosy (cf. Leviticus 12-15). A person also purified himself with water before entering the Temple precincts, offering prayer and sacrifice, and eating. For this reason, in the Courtyard of the Priests (the area before the actual Temple building) was the Laver, an immense bronze basin filled with water. Here the priests purified their hands and feet before offering sacrifices at the nearby altar, bathed before entering the Temple itself, and also drew water for other purifications prescribed in Jewish rituals. Interestingly, the Qumran community, located near the Dead Sea and responsible for producing the Dead Sea scrolls, also had purification pools for the cleansing not only of external "uncleanness" but also of sin.
We too have fonts filled with holy water for blessings for three reasons: as a sign of repentance of sin, for protection from evil, and as a reminder of our Baptism. The repentance of sin symbolized in the washing with water is reflected in Psalm 50: "Have mercy on me, O God, in your goodness; in the greatness of your compassion wipe out my offense. Thoroughly wash me from my guilt and of my sin cleanse me. Cleanse me of sin with hyssop that I may be purified; wash me, and I shall be whiter than snow" (3-4, 9). (Hyssop is a small bush used for sprinkling water). St. John the Baptizer called all to conversion using a ritual washing of water to signify the repentance of sin and purification.
Holy Water (catholiceducation.org)
