Kural - 314

To punish wrong, with kindly benefits the doers ply;
Thus shame their souls; but pass the ill unheeded by

Explanation
The (proper) punishment to those who have done evil (to you), is to put them to shame by showing them kindness, in return and to forget both the evil and the good done on both sides.

Tamil Transliteration
Innaasey Thaarai Oruththal Avarnaana
Nannayanj Cheydhu Vital.