《汉书·传·杜周传》
这时四夷和睦，海内平安，他任职三年，因老病辞职。皇帝优待他，派光禄大夫持节赐给他黄金百斤和酒，又给医药。杜延年病重，皇帝又赐他安车驷马，免官就第。
是时，四夷和，海内平，延年视事三岁，以老病乞骸骨，天子优之，使光禄大夫持节赐延年黄金百斤、酒，加致医药，延年遂称病笃。赐安车驷马，罢就第。
As the four barbarians were peaceful and the empire was at peace, he served in his position for three years before resigning due to old age and illness. The emperor treated him favorably, sending a Grandee of the Imperial Household with a staff to grant him one hundred catties of gold and wine, and also provided him with medicine. When Du Yannian grew seriously ill, the emperor again granted him a carriage and four horses, and allowed him to retire from office.