בַּרְזֶ֣ל בְּבַרְזֶ֣ל יָ֑חַד וְ֝אִ֗ישׁ יַ֣חַד פְּנֵֽי־רֵעֵֽהוּ׃
Afia-se o ferro com o ferro; assim o homem afia o rosto do seu amigo.
Rashi on Proverbs
sharpens the countenance of his friend Heb. יחד, sharpens. Torah scholars sharpen each other in halachah.