Kural - 689

His faltering lips must utter no unworthy thing,
Who stands, with steady eye, to speak the mandates of his king

Explanation
He alone is fit to communicate (his sovereign's) reply, who possesses the firmness not to utter even inadvertently what may reflect discredit (on the latter).

Tamil Transliteration
Vitumaatram Vendharkku Uraippaan Vatumaatram
Vaaiseraa Vanka Navan.