St. John Cassian

He related with regard to another old man living in the desert, that he had asked God to grant him never to become sleepy during a spiritual conference, but, if someone uttered slanderous or useless words, to be able to go to sleep at once, so that his ears should never be touched by that poison. This old man also said that the devil, enemy of all spiritual instruction, works hard to provoke useless words.

He used the following example, ‘Once when I was talking to some brothers on a helpful topic, they were overcome by sleep so deep, that they could not even move their eyelids any longer. Then, wishing to show them the power of the devil, I introduced a trivial subject of conversation. Immediately, they woke up, full of joy. Then I said to them with many sighs, “Until now, we were discussing heavenly things and your eyes were heavy with sleep, but when I embarked on a useless discourse, you all woke up with alacrity. Therefore, brothers, I implore you to recognize the power of the evil demon; pay attention to yourselves, and guard yourselves from the desire to sleep when you are doing or listening to something spiritual. - From the Sayings of the Desert Fathers

St. Ephraim the Syrian

The good God grants us the enlightenment of knowledge, and His grace ever visits our hearts. If she finds peace there, she enters and dwells constantly in the soul. But if she does not find the heart pure, she immediately withdraws. Yet compassion encourages her to descend anew and visit us sinners, for we are all inconstant because of our free will but not by our nature.

We are always distracted and weak, envious and wicked; often do we think evil of one another; we occupy ourselves with wicked ideas, and are plunged in a mire of unclean thoughts. Thus when grace comes to visit us and encounters in our hearts the stench of unclean thoughts, she immediately withdraws without seeking an entrance, that she might make her habitation there and dwell in us, as is pleasing to her. She leaves only a trace of her radiant sweetness in heart, so that one might recognize that grace has visited him but not found an entrance, and, having delighted in grace’s radiance, might seek her out. Do you see God’s Providence? Do you see Christ’s loving-kindness? Do you see how God Who is Holy ever loves us and wants us to be saved?

Blessed is the man who ever strikes to prepare a pure heart for grace, that when she comes she might find the fragrance of virtues and a sacred place in the soul and reside therein unto the ages of ages. - Psalm 114 of the Spiritual Psalter (Or reflections On God) of St. Ephraim

St. Porphyrios

In the eyes of God, the married and the unmarried are the same, provided they live in accordance with the commandments of God and provided they live the life of God. Chastity, lack of possessions and poverty, which are the virtues of the monk, are to be found in a person’s heart. Someone who may be a virgin as far as the body is concerned, but be like an inveterate whore as far as the soul is concerned on account of his malice and passions. Someone may own a dozen houses and yet in his soul be liberated from material things and live like someone who owns nothing. On the other hand, someone may be poor in an external sense, but not free of possessions internally. It is not the quantity of possessions that makes someone propertied or unpropertied, but the attachment of the heart.