Greek Orthodoxy - Theophany

As a great feast, Theophany includes a whole cycle of liturgical services. On the Forefeast of Theophany (January 5), we read according to tradition the Great Hours, a prayer service consisting of many hymns, psalms and other readings from the Old and New Testaments. After the Great Hours, the Great Vespers of Theophany combined with the Liturgy of St. Basil is celebrated. All these services are then combined with the special rite of the Blessing of the Waters, a rite which is repeated on the Feast of Theophany following Matins and the Liturgy of St. John Chrysostom.

The Blessing of the Waters on the Forefeast of Theophany is sometimes called the Small Blessings of the Waters (mikros agiasmos) and on the Feast of Theophany it is called the Great Blessing of the Waters (megas agiasmos). Both are exactly the same, however, and have the same value. It is done twice probably because of the great throngs of people who traditionally came to receive holy water. A sign of sanctification by God’s grace, the blessed water is sprinkled throughout the Church, on the congregation and on each Orthodox Christian individually. It may also be drunk. On the Feast of Theophany and on subsequent days all the faithful, their homes, and often their fields, gardens, and other possessions are traditionally sprinkled with holy water by the priest.

From the book:    
A Year of the Lord