Kural - 748

Howe'er the circling foe may strive access to win,
A fort should give the victory to those who guard within

Explanation
That is a fort whose inmates are able to overcome without losing their ground, even abler men who have besieged it.

Tamil Transliteration
Mutraatri Mutri Yavaraiyum Patraatrip
Patriyaar Velvadhu Aran.