《汉书·传·景十三王传》
御医送药来，太子刘勃不自尝药，又不留宿侍奉疾病。
医进药，太子勃不自尝药，又不宿留侍疾。
When the imperial physician came with medicine, Crown Prince Liu Bo neither tasted the medicine himself nor stayed overnight to tend to the sick man.