כַּ֭מַּיִם הַפָּנִ֣ים לַפָּנִ֑ים כֵּ֤ן לֵֽב־הָ֝אָדָ֗ם לָאָדָֽם׃
As in water face answereth to face, So the heart of man to man.
Rashi on Proverbs
is the heart of a man to a man his friend. According to how much a man knows that his friend loves him, so he will show him his face.