Kural - 471

The force the strife demands, the force he owns, the force of foes,
The force of friends; these should he weigh ere to the war he goes

Explanation
Let (one) weigh well the strength of the deed (he purposes to do), his own strength, the strength of his enemy, and the strength of the allies (of both), and then let him act.

Tamil Transliteration
Vinaivaliyum Thanvaliyum Maatraan Valiyum
Thunaivaliyum Thookkich Cheyal.