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.
If the highest aim of virtue is that which aims at the advancement of most, gentleness is the most lovely of all, which does not hurt even those whom it condemns, and usually renders them whom it condemns worthy of absolution.
When your brother is disturbed and reacts to what you say to him, control your tongue lest you speak even one word in wrath and do not allow yourself to be arrogant concerning him in your heart but remember that he is your brother, a member of Christ and an image of God, influenced by the common enemy. Be merciful and show pity on him because it is possible that the devil through your wrath, will capture his soul and mortify it in resentment and thus, through your carelessness, the soul for whom Christ died is lost (1 Cor. 5:11).
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.