Iron Sharpens Iron.
As iron sharpens iron, So a man sharpens the countenance of his friend. Proverbs 27:17 NKJV
This intimates both the pleasure and the advantage of conversation. One man is nobody; nor will poring upon a book in a corner accomplish a man as the reading and studying of men will. Wise and profitable discourse sharpens men's wits; and those that have ever so much knowledge may by conference have something added to them. It sharpens men's looks, and, by cheering the spirits, puts a briskness and liveliness into the countenance, and gives a man such an air as shows he is pleased himself and makes him pleasing to those about him. Good men's graces are sharpened by converse with those that are good, and bad men's lusts and passions are sharpened by converse with those that are bad, as iron is sharpened by its like, especially by the file. Men are filed, made smooth, and bright, and fit for business (who were rough, and dull, and inactive), by conversation. This is designed, to recommend to us this expedient for sharpening ourselves, but with a caution to take heed whom we choose to converse with, because the influence upon us is so great either for the better or for the worse.
To direct us what we must have in our eye in conversation, namely to improve both others and ourselves, not to pass away time or banter one another, but to provoke one another to love and to good works and so to make one another wiser and better. - Matthew Henry