From Sima Qian's 《
报任安书》:
人固有一死,或重于泰山,或轻于鸿毛,用之所趋异也. Sima Qian wrote it to Ren An after suffering castration, defending why he chose to endure disgrace and live on - to finish the 《
史记》. Mao Zedong quoted it in 《
为人民服务》 mourning Zhang Side, making the line a household saying.