Kural - 465

With plans not well matured to rise against your foe,
Is way to plant him out where he is sure to grow

Explanation
One way to promote the prosperity of an enemy, is (for a king) to set out (to war) without having thoroughly weighed his ability (to cope with its chances).

Tamil Transliteration
Vakaiyarach Choozhaa Thezhudhal Pakaivaraip
Paaththip Patuppadho Raaru.