Kural - 685

In terms concise, avoiding wrathful speech, who utters pleasant word,
An envoy he who gains advantage for his lord

Explanation
He is an ambassador who (in the presence of foreign rulers) speaks briefly, avoids harshness, talks so as to make them smile, and thus brings good (to his own sovereign).

Tamil Transliteration
Thokach Chollith Thoovaadha Neekki Nakachcholli
Nandri Payappadhaan Thoodhu.