Holy water is water that has been blessed by a member of the clergy or by a religious figure. The use for cleansing prior to a baptism and spiritual cleansing is common in several religions, from Christianity to Sikhism. The use of holy water as a sacramental for protection against evil is common among Anglicans, Roman Catholics, and Eastern Christians.
The traditional use of holy water is condemned by evangelical and fundamentalist Christians as a pagan superstition inspired by Satan, based on the ignorant faith of an object having magical powers. They point out that another word for superstition is “idolatry”, saying that we should get our faith not from objects or rituals of man-made origin, but from the one true God who gives eternal life.“See to it that no one takes you captive through hollow and deceptive philosophy, which depends on human tradition and the basic principles of this world rather than on Christ. For in Christ all the fullness of the Deity lives in bodily form, and you have been given fullness in Christ, who is the head over every power and authority”.[1]This text used in Protestant evangelical and fundamentalist objection to ancient orthodox catholic Christian practice is fundamentally a denial that God uses matter as a vehicle for spiritual blessing.
Traditionally, fonts of holy water are placed near the entrances of 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. The Book of Numbers commanded the use of holy water in the "ordeal" for a charge of adultery[2]. The priests and levites were commanded to wash in the laver of water[3] to purify themselves before entering to offer sacrifice of worship in the Tabernacle, Temple of Jerusalem, the assembly of the Lord [4], and Heaven itself.
Catholic Heresies and Traditions (the Boettner List)
Enmity, Prejudice, Putting words in someone's mouth, Polemic, Misrepresentation, Slander, Calumny, Detraction, Scandal
ex opere operato and ex opere operantis
Salvation: declarational salvation and ontological salvation
What does the Bible say about superstitions? (gotquestions.org)
Holy Water (catholiceducation.org)
8 Ways To Use Holy Water | GetFed (getfed.com)
How To Use Holy Water: 10 Ways To Use Holy Water To Sanctify Your Life