The Jesus Prayer is a brief invocation of the name of Jesus, repeated with attention until it becomes the heart’s continuous prayer, in fulfilment of the call to pray without ceasing. It is central to hesychasm and was popularized by the nineteenth-century Russian Way of a Pilgrim.
Jesus Prayer
“Lord Jesus Christ, Son of God, have mercy on me”: the short prayer repeated unceasingly in Eastern Christian practice.
Also: Prayer of the Heart