分別功德論 2.6

2.6

死念者，念人福盡命終時見地獄瑞驚恐失糞。若見餓鬼、若見畜生，隨行所墮，見皆恐怖。意欲捨去，反為對所牽。若當生人，緣父母會。若受男胎，愛彼女人；若受女胎，愛彼男子。除其疾難，三事不差，便得入胎。既受，又認以為己有，七日一變巧風刻割，至三十八七乃成其形。若生天上，天樂來迎，不勝喜悅即失小便。此五道瑞各有所見。此之死應行者，已為明戒深惟無常，命速若電若雲過庭，老病死來無不逝喪。常念此變以自覺悟，故曰死念也。

As for "mindfulness of death", it means being mindful of when a person's merit is exhausted and life ends: seeing the omens of hell, they lose their feces in terror. If they see hungry ghosts or animals, depending on where their actions cause them to fall, all they see is terrifying. Their mind wishes to cast it off and leave, but instead they are dragged by their karmic retribution. If they are to be born as humans, it depends on the union of parents. If taking birth in a male womb, they feel love for that woman; if taking birth in a female womb, they feel love for that man. Removing their sickness and difficulties, when the three conditions do not err, they then enter the womb. Having received it, they further grasp it as their own; changing every seven days, the skillful wind carves and cuts it, until in thirty-eight periods of seven days its form is finally completed. If born in the heavens, heavenly music comes to welcome them, and overcome with joy they immediately lose their urine. These omens of the five destinies each have what is seen. One who should practice this death has already taken it as a clear precept, deeply contemplating impermanence: life is as swift as lightning or a cloud passing through a courtyard, and when old age, sickness, and death arrive, there is none who does not pass away. Constantly being mindful of this transformation to awaken oneself: therefore it is called mindfulness of death.