As a man cannot remain unscathed who spares his enemy on the field of battle, so a man engaged in spiritual warfare cannot save his soul if he spares his body.
Charity, temperance, contemplation, and prayer please God; gluttony, licentiousness, and what multiplies them, please the flesh. Therefore they who are in the flesh cannot please God. And they that are Christ’s have crucified their flesh with the passions and concupiscences.
When the flesh flourishes, the soul fades; when the flesh has full liberty, the soul is straitened; when the flesh is satiated, the soul hungers; when the flesh is adorned, the soul is deformed; when the flesh overflows with laughter, the soul is surrounded by misfortune; when the flesh is in the light, the soul is in darkness...
Do you wish to honor the Body of the Savior? Do not despise it when it is naked. Do not honor it in church with silk vestments while outside it is naked and numb with cold. He who said, 'This is my body,' and made it so by his word, is the same that said, 'You saw me hungry and you gave me no food. As you did it not to the least of these, you did it not to me.' Honor him then by sharing your property with the poor. For what God needs is not golden chalices but golden souls.
No one can say, 'I am poor and hence I have no means of giving alms.' For even if you cannot give as the rich gave their gifts into the temple treasury, give two farthings as the poor widow did, and from you God will consider it greater gift than the gifts of the rich. And if you do not have as much as two farthings? You can take pity on the sick and give alms by ministering to them. And if you cannot do even this? You can comfort your brother by your words. 'A good word is better than the best of gifts.'
Having guarded ourselves against distractions and worries, let us turn our attention to our body on which mental vigilance is completely dependent. Human bodies differ widely from one another in strength and health. Some by their strength are like copper and iron; others are frail like grass. For this reason everyone should rule his body with great prudence, after exploring his physical powers. For a strong and healthy body, special fasts and vigils are suitable; they make it lighter, and give the mind a special wakefulness. A weak body should be strengthened by food and sleep according to one's physical needs, but on no account to satiety. Satiety is extremely harmful even for a weak body; it weakens it, and makes it susceptible to disease. Wise temperance of the stomach is a door to all the virtues. Restrain the stomach, and you will enter Paradise. But if you please and pamper your stomach, you will hurl yourself over the precipice of bodily impurity, into the fire of wrath and fury, you will coarsen and darken your mind, and in this way you will ruin your powers of attention and self-control, your sobriety and vigilance…