《汉书·传·佞幸传》
皇帝看到红阳侯立的态度前后变化极大，知道其中必有蹊跷，于是派有关部门查验此事。
于是天子疑焉，下有司案验。
The Emperor noted that the Marquis of Hongyang had drastically changed his attitude and knew that something was amiss. As a result, he dispatched officials to look into the matter.