《宋书·列传·卷六十四》
秋冬时节收割完毕，人民进入城堡，用以防备盗贼，使防御有素。
旧秋冬收敛，民人入保，所以警备暴客，使防卫有素也。
In the autumn and winter, when harvesting is complete, the people will enter the castle, to guard against thieves, to make their defense in good order.