话说三国时期，曹操挟天子以令诸侯，权倾朝野。他表面上礼贤下士，广纳贤才，实则心怀叵测，暗中排除异己。一次，曹操宴请众多文武大臣，席间，他突然问众人：‘你们说，这世上最可怕的是什么？’大臣们纷纷猜测，有的说猛兽，有的说瘟疫，有的说天灾。曹操却神秘一笑，说：‘都不是，最可怕的是人心叵测！’话音刚落，他便命人将早已埋伏好的武士将几个反对他的大臣逮捕。众人这才明白，曹操的看似友好和善的外表下，隐藏着无比阴险的用心。曹操此举不仅震慑了朝中反对势力，更让世人见识了他居心叵测的狠辣手腕，也为后世留下了‘居心叵测’的警示。从此，这个成语便用来形容那些内心险恶、难以捉摸的人。
hua shuo sanguo shiqi, caocao xietianzi yiling zhuhou, quan qing chaoyao. ta biaomianshang li xian xia shi, guang na xiancai, shize xinhuai po ce, anzhong paichu yiji. yici, caocao yanqing zhongduo wenwu dacheng, xijian, ta turan wen zhongren: 'nimen shuo, zhe shi shang zui kepa de shi shenme?' dachengmen fenfen caice, you de shuo mengshou, you de shuo wenyi, you de shuo tian zai. caocao que shenmi yixiao, shuo: 'dou bushi, zui kepa de shi renxin po ce!' huayin gangluo, ta bian mingren jiang zaoyi maofu hao de wushi jiang jige fandui ta de dacheng daibao. zhongren caicai mingbai, caocao de kansi youhao heshan de waibiao xia, yincangzhe wubi yinxian de yongxin. caocao ci ju bujin zhenshe le chao zhong fandui shili, geng rang shiren jianshi le ta juxinpoce de henla shouwan, ye wei houshi liu xia le 'juxinpoce' de jingshi. congci, zhege chengyu bian yong lai xingrong na xie neixin xian'e, nan yi zhumo de ren.