St. John Climacus
“Intelligent silence is the mother of prayer, freedom from bondage, custodian of zeal, a guard on our thoughts, a watch on our enemies, a prison of mourning, a friend of tears, a sure recollection of death, a painter of punishment, a concern with judgment, servant of anguish, foe of license, a companion of stillness, the opponent of dogmatism, a growth of knowledge, a hand to shape contemplation, hidden progress, the secret journey upward.”
Source: St. John Climacus, The Ladder of Divine Ascent