What is the tradition of hidden prayer among the monastic Fathers?

Here are some excerpts from the “Paradise of The Holy Fathers” and other monastic writings:

“A brother asked an elder: ‘What is meant by the cultivation of the soul that brings forth fruits?’ He answered: ‘Cultivating the soul signifies silence, unceasing prayer, control of desires, toil of the flesh, and refraining from noticing people’s sins and only remembering one’s own shortcomings and sins. Whenever someone is steadfast in these virtues, his soul will be successful and will grow and bring forth fruits.’”

291 St. Augustine of Hippo, Expositions on the Book of Psalms 86.7 (NPNF I/8:412) amended.

“An elder said: ‘When a monk is truly struggling, God wants him not to be attached to anything in this world, not even a single needle, so that his thoughts may be focused on remembering our Lord Jesus Christ and repenting from his sins.’”

“An elder said: ‘Acquire silence with discernment. Be concerned only with God and do not be concerned with anything that is earthly. Examine all your dealings in your rising up and your sitting down. Trust in God and do not be afraid of the wicked.’”

“One of the saints once said: ‘The Fathers have handed down this path to us: to work with our hands, to remain silent and to weep over our sins.’”

St. John Cassian — who recorded for us a vivid portrait of the Egyptian monastic life of his time — saw a correlation between the reading of scripture and fervent prayer. Each of these supports the other through the work of the Holy Spirit. Note that the two works of Cassian, “The Institutes” and “The Conferences” both extensively quote scripture. He emphasized that the kingdom of God is the ultimate goal of spiritual life, and that reading and contemplating upon the words of scripture serve to attain that goal. He dedicated his Conferences 9 and 10, and chapters 2 and 3 of The Institutes to the topic of prayer. He says that the prayers of the canonical hours are compulsory for the monk, and that it is the labor of the monk to transform the recitation of the psalms into personal prayers that feed his relationship with God, his God. Similarly, in studying the Holy Bible, the monk cannot be content with merely reading or reciting, but must transform the texts into contemplations emanating from his depths, so that the words of the Holy Bible seem to emerge from him as his own personal prayers.²⁹²

292 St. John Cassian, The Conferences 14.10 (NPNF II/11:439–440).