《资治通鉴·陈纪·陈纪九》
李穆上表请求辞职归养，隋文帝下诏书说： 古代姜太公吕尚以百岁高龄辅佐周文王、武王成就王业，张苍以白发老人担任汉文帝的丞相，高才伟人佐命当世，不能拘泥于常礼。 
李穆上表乞骸骨，诏曰： 吕尚以期颐佐周，张苍以华皓相汉，高才命世，不拘常礼。 
Li Mu submitted a memorial requesting to resign and retire to support his parents, and the Emperor Wen of the Sui dynasty issued an edict saying: "In ancient times, Jiang Taigong and Lu Shang were able to assist King Wen and King Wu of the Zhou dynasty in achieving their great cause at the age of one hundred, Zhang Cang was able to serve as the prime minister for Emperor Wen of Han with white hair. Great talents should serve the current era and should not be confined by conventional rites.