Kural - 417

Not e'en through inadvertence speak they foolish word,
With clear discerning mind who've learning's ample lessons heard

Explanation
Not even when they have imperfectly understood (a matter), will those men speak foolishly, who have profoundly studied and diligently listened (to instruction).

Tamil Transliteration
Pizhaith Thunarndhum Pedhaimai Sollaa Rizhaiththunarn
Theentiya Kelvi Yavar.