Christ told His friends, that is, His disciples, to beware of the leaven of the Pharisees and scribes, meaning by leaven their false pretence. For hypocrisy is a thing hateful to God, and abominated by man, bringing no reward, and utterly useless for the salvation of the soul, or rather the cause of its perdition. Though sometimes it may escape detection for a little, yet before long it is sure to be laid bare and bring disgrace upon them, like ill-featured women, when they are stripped of that external embellishment which they had produced by artificial means. Hypocrisy, therefore, is a thing foreign to the character of the saints. That it is impossible for those things that are done and said by us to escape the eye of the Deity, He showed by saying: “There is nothing covered that shall not be revealed; neither hid that shall not be known.” For all our words and deeds shall be revealed at the day of judgment.
The view we take of our Savior's dispensation is the view of the holy fathers who preceded us. By reading their works we equip our own mind to follow them and to introduce no innovation into Orthodoxy.
Even a pious person is not immune to spiritual sickness if he does not have a wise guide -- either a living person or a spiritual writer. This sickness is called prelest, or spiritual delusion, imagining oneself to be near to God and to the realm of the divine and supernatural. Even zealous ascetics in monasteries are sometimes subject to this delusion, but of course, laymen who are zealous in external struggles (podvigi) undergo it much more frequently. Surpassing their acquaintances in struggles of prayer and fasting, they imagine that they are seers of divine visions, or at least of dreams inspired by grace. In every event of their lives, they see special intentional directions from God or their guardian angel. And then they start imagining that they are God's elect, and often try to foretell the future. The Holy Fathers armed themselves against nothing so fiercely as against this sickness -- prelest.
If a man purifies his heart and uproots from it all sin against the Lord; if he labors diligently to acquire Divine knowledge and succeeds in seeing with his mind that which is invisible to many, he must not through this exalt himself over others. Who among creatures is purer than an incorporeal being and who has more knowledge than an Angel? Yet, having exalted himself he was cast down from heaven like lightning. His pride was regarded by God as impurity.
Pray before your body takes rest on your bed... If you are tempted, make the Sign (of the Cross) on your forehead reverently… for this is a known and tested weapon against the Devil.
Prayer... by its action it is the reconciliation of man with God, the mother and daughter of tears, a bridge for crossing temptations, a wall of protection from afflictions, a crushing of conflicts, boundless activity, the spring of virtues, the source of spiritual gifts, invisible progress, food of the soul, the enlightening of the mind, an axe for despair, a demonstration of hope, the release from sorrow.
Fasting needn't be limited to abstinence from food alone, because true fasting is departure from evil deeds. Forgive your neighbor any insult, abstain from causing your neighbor offence, abstain from irritation, from senseless sorrows, from fear, wrath, and so on. ‘True fasting is alienation from evil, temperance of the tongue, setting aside of wrath, casting out of lust, idle talk, lies, and oath-breaking’…This is a true and pleasing fast for the Lord. Departing from these vices and from a corrupt state is what comprises a true fast.
Our works in this life are the sowing, and the future life is the harvest of what we have sown. Whatever one sows here, that is what he shall reap there. If one hastens to cultivate the field of his heart, to fertilize it and to sow in it the seeds of immortal grain, he can confidently expect to see a corresponding harvest unto eternal rest and delight. He that sows with tears of repentance shall reap with rejoicing and 'shall be filled,' says the Prophet (Psalms 16:16 and 125:6), for sweet rest follows upon the labors of piety. But rest and refreshment are denied to him who has not labored in the work of piety-he that is idle should not eat, it is said (cf. II Thessalonians 3:10).
Having filled himself with pride, the Antichrist will begin to set himself up and glorify himself as God, belching forth slander against Christ. He will do this so openly that he will command that all those who do not want to serve him as God be killed.
To wage war only with the sins that make their appearance as actual deeds would be just as unsuccessful as cutting down weeds in a garden instead of digging them up at the root and throwing them out. Sins appear as inevitable outgrowths from their roots, the passions of the soul.
He therefore, the God Who rules over all things, must stretch out a saving hand to the wandering sheep, whom the Supreme Shepherd has now in fact redeemed. For He looked for it as it wandered afar, and He has placed it in a secure sheepfold, safe against thieves and wild beasts: namely, His Church.
Unless the inner man meditates upon the law of God and is nourished thereby, unless he is strengthened by reading and by prayer, he is conquered by the outer man, and he serves his master.