Albert Barnes Commentary Proverbs 27:19

"As in water face [answereth] to face, So the heart of man to man." — Proverbs 27:19 (ASV)

As we see our own face when we look upon the mirror-like surface of the water, so in every human heart we may see our own likeness. In spite of all diversities, we come upon the common human nature in which we all alike share. Others see in the reference to the reflection in the water the thought that we judge others by ourselves, find them faithful or the opposite, as we ourselves are.