《后汉书·列传·袁绍刘表列传下》
曹操和袁绍在官度互相对峙时，袁绍派人要求援助，刘表答应了，但没派兵去，也不增援曹操，而且想静观天下的变化。
及曹操与袁绍相持于官度，绍遣人求助，表许之，不至，亦不援曹操，且欲观天下之变。
When Cao Cao and Yuan Shao confronted each other in Guandu, Yuan Shao sent someone to ask for help, and Liu Biao agreed, but did not send troops, nor did he reinforce Cao Cao, and wanted to take a wait-and-see approach to the changes in the world.