Holy water is water that has been blessed by a member of the clergy or 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 and Roman Catholics.
In Catholicism, Anglicanism, Eastern Orthodoxy, Oriental Orthodoxy and some other churches, holy water is water that has been sanctified by a priest for the purpose of baptism, the blessing of persons, places, and objects, or as a means of repelling evil.
The use of holy water in the earliest days of Christianity is attested to only in somewhat later documents. The Apostolic constitutions, which go back to about the year 400, attribute the precept of using holy water to the Apostle Matthew. It is plausible that in earliest Christian times water was used for expiatory and purificatory purposes in a way analogous to its employment in Jewish Law. Yet, in many cases, the water used for the Sacrament of Baptism was flowing water, sea or river water, and it could not receive the same blessing as that contained in the baptisteries in the view of the Roman Catholic church. However, Eastern Orthodox do perform the same blessing, whether in a baptistry or an outdoor body of water.