Kural - 157

Though others work thee ill, thus shalt thou blessing reap;
Grieve for their sin, thyself from vicious action keep

Explanation
Though others inflict injuries on you, yet compassionating the evil (that will come upon them) it will be well not to do them anything contrary to virtue.

Tamil Transliteration
Thiranalla Tharpirar Seyyinum Nonondhu
Aranalla Seyyaamai Nandru.