Thirukkural

காணாதான் காட்டுவான் தான்காணான் காணாதான் கண்டானாம் தான்கண்ட வாறு.

Kaanaadhaan Kaattuvaan Thaankaanaan Kaanaadhaan Kantaanaam Thaankanta Vaaru

One who would teach a fool will (simply) betray his folly; and the fool would (still) think himself "wise in his own conceit"