Our holy fathers have renounced all other spiritual work and concentrated wholly on this one doing, that is, on guarding the heart, convinced that, through this practice, they would easily attain every other virtue, whereas without it not a single virtue can be firmly established.
If someone is judged worthy to receive the gift of knowledge but allows his heart to be full of bitterness or rancor or aversion to another, it is as if he had been struck in the eye by a thornbush. That is why knowledge is no good without charity.
An old man was asked, 'How can I find God?' He said, 'In fasting, in watching, in labors, in devotion, and, above all, in discernment. I tell you, many have injured their bodies without discernment and have gone away from us having achieved nothing. Our mouths smell bad through fasting, we know the Scriptures by heart, we recite all the Psalms of David, but we have not that which God seeks: charity and humility.'
If you have received from God the gift of knowledge, however limited, beware of neglecting charity and temperance. They are virtues which radically purify the soul from passions and so open the way of knowledge continually.
Men who are leading a spiritual life see by the eyes of their heart how the devil lays his snares, how the angels guide us, and how the Lord, in His Sovereign power, allows the temptations, and how he comforts.
What is it that commends our own life? Is it miracles, or is it a life scrupulously and uprightly lived? It is rather from the latter that miracles arise, and to that they tend. For he that lives a worthy life, draws this grace upon himself; and whosoever receives such graces receives them that he may help others to amend their lives. For even Christ wrought miracles that He might the more be accepted as worthy of belief, and so might the more attract men to Himself, and by this means bring sanctity into their lives.