Kural - 867

Unseemly are his deeds, yet proffering aid, the man draws nigh:
His hate- 'tis cheap at any price- be sure to buy

Explanation
It is indeed necessary to obtain even by purchase the hatred of him who having begun (a work) does what is not conductive (to its accomplishment).

Tamil Transliteration
Kotuththum Kolalventum Mandra Atuththirundhu
Maanaadha Seyvaan Pakai.