Bhaṭṭikāvya 12.52

12.52

durgā''śritānāṃ bahunā 'pi rājan ! kālena pārṣṇigrahaṇā''di-hetuḥ
durgoparodhaṃ na ca kurvato 'sti śatroś cireṇā 'pi daśā''sya ! hāniḥ

For those who take refuge in fortresses, O King, even after much time, there is a reason for an attack in the rear and the like;
nor is there any loss, even after a long time, O Ten-Faced One, for the enemy who lays siege to the fortress.