Kautilya's Arthashastra 2.15.22

2.15.22

tato 'rdham āpadarthaṃ jānapadānāṃ sthāpayed, ardham upayuñjīta //

Of the store, thus, collected, half shall be kept in reserve to ward off the calamities of the people and only the other half shall be used. Old collection shall be replaced by new supply.