St. Theodoros The Great Ascetic - 34 -36

34. We have been instructed to keep vigil - with prayers, readings, and the recitation of the Psalter - at all times, and especially at feasts. A monk who keeps vigil refines his mind for contemplation, whereas much! sleep coarsens the intellect. But take care that during vigils you do not pass the time in empty gossip or evil thoughts. It is better to be asleep than to keep vigil with vain words and thoughts.

35. He who keeps a serpent in his breast and he who keeps an evil thought in his heart will both be killed, the one by being bitten in the body by venomous fangs and the other by injecting a lethal poison into his soul. Let us, then, speedily slay the 'offspring of vipers' (Matt. 3:7), and let us not bring forth evil thoughts from our heart, lest we suffer bitter pangs.

36. A pure soul can truly be called a 'chosen vessel' (Acts 9:15), 'an enclosed garden', 'a sealed fountain' (Song of Solomon 4:12), and 'a throne of perceptiveness' (Prov. 12:23. LXX). But a soul polluted with filthy impurities stinks like a sewer.