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.
But if you give a strong body rest and ease and idleness, all the passions dwelling in the soul are intensified. Then, even if the soul has a great desire for good, even the very thought of the good that is desired will be taken from you.
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.
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.