Thirukkural 650

இணருழ்த்தும் நாறா மலரனையர் கற்றது உணர விரித்துரையா தார்.

iNaruzhththum nARa malaranaiyer kaRRathu uNara virithuraiyadhAr.

Those who have learned but do not explain their knowledge plainly are like flowers that yield no fragrance, even when crushed.