St. Sabbas of Kalymnos: On what it means to be a monk

 A monk is one who suffers and weeps for his own sins and who pays no attention to the sins of others; who does not judge or get angry, but who endures patiently, with pleasure, every wrong and all contempt in order to achieve intimacy with God, the heavenly Judge and Father of all.

+St. Sabbas of Kalymnos, quoted in The Synaxarion, volume 4, his entry on April 7.

Elder Ephraim of Philotheou: On Watchfulness

 Abba Paphnutios was a renowned desert father. One day as he was walking, he noticed two people committing a certain sin. A sinful though assailed him: "Look at the great evil they are doing!" He saw them with his own eyes and was immediately bombarded by this thought, which attempted to assault the saint's pure soul by pushing him either to criticize or to become scandalized. However, being practiced in watchfulness, he immediately perceived the assault and responded to himself, "They are sinning today; I will sin tomorrow. They will repent, but I am a hard-hearted, unrepentant, and prideful man. I will not repent, and I will end up in Hell. Truly, I am worse than these two people. I am full of passions; therefore, what can I say about these people who are less sinful than me?" By thinking this way, he brought the sinful invitation to a dead stop and avoided condemning the people who were transgressing.

He did not walk much further when an angel of God appeared before him, holding a double-edged sword dripping with blood. The angel asked him, "Paphnutios, do you see this sword? Do you see the blood that is dripping?"

"I see it, O angel of God."

"With this sword, I execute and behead them who judge their fellow man. Since you did not judge the two people who were indeed sinning - not just ones whom you suspected to be sinning, but whom you actually saw with your very own eyes - but condemned yourself instead, your name has been written in the book of eternal life."

+Elder Ephraim of Philotheou, from The Art of Salvation, homily 11 on Watchfulness, Prayer, and Confession

St. Seraphim of Sarov: Do not Judge your Neighbor

We must not Judge anyone, even if with our own eyes we have seen someone sinning, or walking in transgression of God's commandments. For according to the word of God: "Judge not, that ye be not judged" (Matt 7:1), and again: "Who art thou that judgest another man's servant? To his own master he standeth of falleth; yea, he shall be holden up: for God is able to make him stand" (Rom 14:4).
It is much better always to bring to mind these words of the Apostle: "Let him that thinkest he standeth take heed lest he fall" (1 Cor 10:12).
For we do not know how long we may remain in virtue, as says the Prophet who attained to knowledge of this matter by experience: "In my prosperity I said, I shall never be moved. Thou didst hide Thy face, and I am troubled" (Ps 29:7-8).
+St. Seraphim of Sarov, from Spiritual Instructions, Instruction XX Do not Judge your Neighbor, in Little Russian Philokalia, Vol 1: St. Seraphim.

Abba Isaiah of Scetis: Not judging one's neighbor

Not judging one's neighbor is a protection for those who struggle in knowledge, but blaming one's neighbor destroys this protection in ignorance. Taking care of one's tongue¹ is the sign a person who practices the virtues. Not controlling one's tongue shows that a person has no inner virtue. Goodness gives rise to purity. Distraction give rise to passions, and hardheartedness gives rise to anger. Discipline of the soul is hatred of distraction, and disciple of the body is poverty. The fall of the soul is loving distraction, and its rise is silence in knowledge. Excessive sleep disturbs the passions within the body, and vigil in measure is the heart's salvation. Too much sleep thickens the heart, but vigil in measure refines it. It is better to sleep in silence and knowledge, than to keep vigil with idle talk. Compunction calmly expels all evil. Not offending your neighbor's conscience gives rise to humility. Human glory very gradually gives rise to pride. Loving to boast expels knowledge.
+Abba Isaiah of Scetis, from Ascetic Discourses, Discourse 16 On the Joy that Comes to the Soul that Desires to Serve God.

¹ St. John Climacus, from The Ladder, Step 22

Abba Pior: The small sins of my brother

One day, the fathers of Scetis came together to judge a brother who had grievously sinned. Abba Pior kept silence while they discussed the case, then took a sack, filled it with sand and hoisted it onto his shoulder, he also put a little sand in a small bag that he placed in front of him. When he was asked what this action meant, he said, "This sack that contains a lot of sand is my many sins that I have left behind me, and these are the small sins of my brother that I place in front of me and spend my time judging! Would it not be better to do the opposite?" The father got to their feet edified, and recognized that Abba Pior had chosen the way of salvation.
+from The Synaxarion entry for the Venerable Father Pior, June 17.