金光明最勝王經疏 2.29

2.29

Commentary: This concludes the intent of the preceding doubt. According to this sūtra's text and the third fascicle of the Nirvāṇa [Sūtra], the causes and conditions for long life are all of the myriad practices, because one attains the three bodies. But here he merely adduces giving food and not killing living beings; since these are common causes and conditions for the life-span of sentient beings, he specifically adduces them to ask. He feared that beings, seeing the Buddha's life-span was eighty years, would then doubt that not killing and giving food were not the causes for obtaining a long life. Wishing to make them rely on the body to increase the Path and receive beings, it was convenient [to frame the question this way].