The '''Jesus Prayer''', also called the '''''Prayer of the Heart''''' by some [[Church Fathers]], is a short, simple prayer that has been widely used, taught and discussed throughout the history of [[Eastern Christianity]]. The exact words of the prayer have varied, from a simple form such as [[Kyrie eleison|"Lord, have mercy"]] to the more common extended form: "Lord Jesus Christ, Son of God, have mercy on me, the sinner." The form most in use on [[Mount Athos]] is "Lord Jesus Christ, Son of God, have mercy on me." It is particularly used in the practice of the spiritual life known as [[hesychasm]].