אֵין סַכִּין מִתְחַדֶּדֶת אֶלָּא בְּיֶרֶךְ חֲבֶרְתָּהּ

ביטוי (אנגלית)

A knife is only sharpened by the blade of another knife

הגדרה (אנגלית)

A knife can be sharpened only by another knife. Figuratively: Study in partnership or with a companion enriches the learners and sharpens the mind.

("Iron sharpens iron together (Proverbs 27) – Rabbi Hama bar Hanina said: A knife is only sharpened by the blade of another; so too, a Torah scholar improves only through his fellow" – Genesis Rabbah 69:2)