Kural - 307

The hand that smites the earth unfailing feels the sting;
So perish they who nurse their wrath as noble thing

Explanation
Destruction will come upon him who ragards anger as a good thing, as surely as the hand of him who strikes the ground will not fail.

Tamil Transliteration
Sinaththaip Porulendru Kontavan Ketu
Nilaththaraindhaan Kaipizhaiyaa Thatru.