《墨子·62章 备穴》
同时在隧道内还要注意仔细审听左右两边传来的声响，一旦发现情况，立即设法断绝阻挡敌人向前。
从穴内听穴之左右，急绝其前，勿令得行。
At the same time, pay close attention to the sounds on the left and right sides of the tunnel. If a situation arises, take immediate measures to cut off the enemy's advancement.