Kural - 795

Make them your chosen friend whose words repentance move,
With power prescription's path to show, while evil they reprove

Explanation
You should examine and secure the friendship of those who can speak so as to make you weep over a crime (before its commission) or rebuke you severely (after you have done it) and are able to teach.

Tamil Transliteration
Azhachcholli Alladhu Itiththu Vazhakkariya
Vallaarnatapu Aaindhu Kolal.