Kural - 678

By one thing done you reach a second work's accomplishment;
So furious elephant to snare its fellow brute is sent

Explanation
To make one undertaking the means of accomplishing another (similar to it) is like making one rutting elephant the means of capturing another.

Tamil Transliteration
Vinaiyaan Vinaiyaakkik Kotal Nanaikavul
Yaanaiyaal Yaanaiyaath Thatru.