The Jesus Prayer, also known as The Prayer, is a short formulaic prayer, esteemed and advocated especially in Eastern Christianity and Catholicism:Lord Jesus Christ, Son of God, have mercy on me, a sinner.
Christogram with the Jesus Prayer in Romanian: Doamne Iisuse Hristoase, Fiul lui Dumnezeu, miluieşte-mă pe mine păcătosul ("Lord Jesus Christ, Son of God, have mercy on me, a sinner")
Icon of the Transfiguration of Jesus by Theophanes the Greek (15th century, Tretyakov Gallery, Moscow). Talking with Christ: Elijah (left) and Moses (right). Kneeling: Peter, James, and John
Eastern Christian prayer rope
Christ the Redeemer by Andrei Rublev (c. 1410, Tretyakov Gallery, Moscow)
Hesychasm is a contemplative monastic tradition in the Eastern Christian traditions of the Eastern Catholic Churches and Eastern Orthodox Church in which stillness (hēsychia) is sought through uninterrupted Jesus prayer. While rooted in early Christian monasticism, it took its definitive form in the 14th century at Mount Athos.
Gregory Palamas