Originally from Cyprus, St. Gregory migrated to Palestine where he joined a monastic community on Mount Sinai. Later he moved to Mount Athos in northern Greece where he developed his own method of contemplation that has influenced Christians worldwide. If, for example, you have ever prayed the Jesus Prayer, then the heritage of St. Gregory of Sinai has probably touched your life.
Gregory sought union with God by disciplining the body and quieting the mind. He taught that repetition of the Jesus Prayer opened the soul to the divine presence and led to the highest forms of contemplation. In the following passage, he gives instruction about practicing this prayer:
Some of the fathers taught that the prayer should be said in full: “Lord, Jesus Christ, Son of God, have mercy upon me.” Others advised saying half, thus: “Jesus, Son of God, have mercy upon me”; or “Lord Jesus Christ, have mercy upon me,” or to alternate, sometimes saying it in full and sometimes in a shorter form. Yet it is not advisable to pander to laziness by changing the words of the prayer too often, but to persist a certain time as a test of patience.
Again, some teach the saying of the prayer with the lips, others with and in the mind. In my opinion both are advisable. For at times the mind, left to itself, becomes wearied and too exhausted to say the prayer mentally; at other times the lips get tired of this work. Therefore both methods of prayer should be used—with the lips and with the mind. But one should appeal to the Lord quietly and without agitation, so that the voice does not disturb the attention of the mind and does not thus break off the prayer, until the mind is accustomed to this doing and, receiving force from the Spirit, firmly prays within on its own. Then there will be no need to say the prayer with the lips; indeed, it will be impossible, for he who reaches this stage is fully content with mental doing of the prayer and has no wish to leave it.
Gregory taught his method to monks on Mount Athos and made it a source of contemplative prayer for the church of the East. He traveled to monasteries and dioceses throughout Greece and Macedonia, inviting monks and religious to practice the Jesus Prayer. In Macedonia he also established three colonies of anchorites who were devoted to contemplative prayer.
Gregory wrote extensively, including tracts on asceticism, verses on the nature of God, liturgical hymns, and theological treatises. His most significant work, The 137 Chapters or Spiritual Meditations, spread the practice of disciplined contemplative prayer throughout the East and Europe.