釋淨土群疑論 2.41

2.41

釋曰：諸業不定，或轉重作輕、或促長令短，具如經說，不可備陳。行者本雖受戒願生天中，後遇勝緣歸生淨土。行雖劣弱，以後願強，資前戒品轉增殊勝，與佛願合，壽命遐長阿僧祇劫。如捨福行作其命行，有雖豐財多病命短，捨物入定，捨衣鉢業延彼命根，更增長遠。佛力、法力、願力、業力不可思議，非諸凡夫所度量也。

Explanation: All karmas are indeterminate; some turn the heavy into the light, and some shorten what was long, fully as explained in the sūtras and impossible to recount in full. Although the practitioner originally received the precepts vowing to be born in heaven, later they encountered superior conditions and turned toward rebirth in the Pure Land. Although the practice was inferior and weak, because the later vow is strong, it assists the prior grade of precepts so that they become increasingly superior; matching the Buddha's vow, their lifespan is prolonged to an asaṃkhyeya of kalpas. It is like relinquishing practices of merit to perform practices of life: some people, though wealthy, are sickly and short-lived; by giving away their goods and entering samādhi, or relinquishing their robes and bowl to make karma that extends the faculty of life, their lifespan is increased and lengthened even further. The Buddha's power, the Dharma's power, the power of vows, and the power of karma are inconceivable, beyond the calculation of ordinary beings.