《三国志·魏书·和常杨杜赵裴传》
现在不如让前进逼近重围，派间谍暗中联络曹仁，让他知道外部有援救，以激励将士们。
当今不若前军偪围，遣谍通仁，使知外救，以励将士。
We should let the army besiege the enemy and send spies to contact Cao Ren and let him know that reinforcements are on the way so as to motivate the morale of the troops.