Solomon
Proverbs 27:19KJV·traditional attribution

As in water face answereth to face, so the heart of man to man.

Matthew Henry Presbyterian

This shows us that there is a way, 1. Of knowing ourselves. As the water is a looking-glass in which we may see our faces by reflection, so there are mirrors by which the heart of a man is discovered to a man, that is, to himself. Let a man examine his own conscience, his thoughts, affections, and intentions.

John Gill Reformed Baptist

As the fining pot for silver, and the furnace for gold,.... For the trying, proving, and purifying these metals; see Pro 17:3; so is a man to his praise; or "according to the mouth of his praise" (p); if his own mouth praises him, as in Pro 27:2;, he is known to be what he is, a foolish and vainglorious person: or "so a man...

Jamieson-Fausset-Brown Reformed

We may see our characters in the developed tempers of others.