《资治通鉴·唐纪·唐纪四十五》
对尚未实行的事情，臣下以莫论机要为戒；对已实行的事情，臣下又说不必讽谏已成之事，渐渐地生出了顾忌，动不动就涉及猜疑。由此，人们各自隐瞒真情，以讲话为忌讳，以至于在变乱将起时，万民同忧，只有陛下安然而无所察觉，还在说太平将会到来。
未行者则戒以枢密勿论，已行者又谓之遂事不谏，渐生拘碍，动涉猜嫌，由是人各隐情，以言为讳，至于变乱将起，亿兆同忧，独陛下恬然不知，方谓太平可致。
For matters that had yet to be carried out, the ministers refrained from discussing official matters as a warning; for matters that had already been carried out, the ministers again said that there was no need to criticize that which had already been done. Gradually, scruples arose and suspicion became involved in every move. As such, people concealed their genuine feelings and avoided speaking out, to the point that when change and disruption were about to occur, ten thousand people would be worried, while the emperor alone remained at ease and oblivious, still saying that peace was about to arrive.