人生于地，悬命于天，此人之制命于天也。栽者，培之。倾者，覆之。此天之制命于人
也。天本无二，而以此观之，则有天之天者，谓生我之天，生于无而由乎天也；有人之天者
，谓成我之天，成于有而由乎我也。生者在前，成者在后，而先天后天之义，于斯见矣。故
以人之禀赋言，则先天强浓者，多寿；先天薄弱者，多夭。后天培养者，寿者更寿；后天斫
削者，夭者更夭。
若夫骨骼者，先天也。肌肉者，后天也。精神者，先天也。容貌者，后天也。颜色之有
辨也，苍者寿而妖者夭。嫩中有苍者吉，苍中有嫩者凶。声音之有辨也，充者寿而怯者夭。
虽细而长者吉，虽洪而促者凶。形体之有辨也，坚者寿而脆者夭。身虽羸瘦而动作能耐者吉
，体虽强盛而精神易困者凶。动静有辨也，静者寿而躁者夭。性虽若急而急中有和者吉，阳
虽若浓而阴中蕴薄者凶。至若少长之辨，初虽绵弱而渐长渐坚者，晚成之征也。气质之辨，
少年华丽而易盈易满者，早凋之兆也。是故两天俱得其全者，耆艾无疑也。先后俱失其守者
，夭促弗卜也。
若以人之作用言，则先天之强者不可恃，恃则并失其强矣；后天之弱者当知慎，慎则人
能胜天矣。所谓慎者，慎情志可以保心神，慎寒暑可以保肺气，慎酒色可以保肝肾，慎劳倦
饮食可以保脾胃。惟乐可以养生，欲乐者莫如为善。惟福可以保生，祈福者切勿欺天。但使
表里无亏，则邪疾何由而犯？而两天之权不在我乎？故广成子曰∶毋劳尔形，毋摇尔精，乃可
以长生。至矣哉，两言尽之矣。勿以此为易而忽之。
人依托大地而生，生命悬系于天，这是天对人的命运的主宰。上天对草木，生长良好的加以培育，倾倒败坏的予以覆灭。这是人对天地规律的顺应与反馈。天道本无二致，但从这一现象观察，就有“天之天”和“人之天”的区别。“天之天”，指的是赋予我生命的本源之天，它生于无形，由天所主；“人之天”，指的是成就我形体的后天之天，它成于有形，由我自身主宰。先有生命的诞生，后有后天的成就，先天与后天的含义，在此便显现出来了。因此，从人的禀赋来说，先天禀赋强盛的，多长寿；先天禀赋薄弱的，多夭折。后天注重培养的，长寿者更加长寿；后天肆意耗损的，夭折者更加短命。
至于骨骼，属于先天；肌肉，属于后天。精神，属于先天；容貌，属于后天。面色有辨别，苍劲者长寿而妖艳者夭折。柔嫩中带有苍劲的是吉兆，苍劲中夹杂柔嫩的是凶兆。声音有辨别，洪亮充实者长寿而怯弱短促者夭折。虽然声音细小但悠长的是吉兆，虽然声音洪大但急促的是凶兆。形体有辨别，坚实者长寿而脆弱者夭折。身体虽然瘦弱但动作能持久的是吉兆，体质虽然强壮但精神容易困倦的是凶兆。动静有辨别，安静者长寿而急躁者夭折。性格虽然看似急躁但急躁中蕴含平和的是吉兆，阳气虽然看似强盛但阴精中蕴藏薄弱的是凶兆。至于少长的辨别，起初虽然绵软微弱但逐渐成长逐渐坚固的，是晚成的征兆。气质的辨别，少年时期华丽张扬且容易自满的，是早凋的预兆。因此，先天与后天都具备完备条件的，无疑是大寿之人。先天与后天都失去守持的，短命夭折是不用占卜就能知道的。
如果从人的主观作用来说，先天强盛的人不可倚仗，一旦倚仗就会同时失去其强盛的优势；后天虚弱的人应当知道谨慎，谨慎则人能战胜天命。所谓谨慎，就是谨慎情志可以保养心神，谨慎寒暑变化可以保养肺气，谨慎酒色可以保养肝肾，谨慎劳倦和饮食可以保养脾胃。只有快乐可以养生，想要获得快乐没有比行善更好的了。只有福气可以保全生命，祈求福气千万不要欺骗上天。只要使表里没有亏损，那么邪气疾病从哪里侵犯呢？而先天与后天的权柄不就在我们手中吗？所以广成子说：“不要劳累你的形体，不要摇动你的精气，这样就可以长生。”说得真好啊，这两句话概括尽了道理。不要因为这件事容易就忽视它。
Human beings are born relying on the earth, and their life is suspended from Heaven; this is how Heaven governs human destiny. For those that are upright, Heaven nourishes them; for those that are leaning or falling, Heaven overturns them. This represents the interaction between Heaven and humanity. Although the Dao of Heaven is singular, observing it reveals two aspects: "Heaven's Heaven" and "Human's Heaven." "Heaven's Heaven" refers to the Heaven that gives birth to me, originating from non-being and governed by Heaven. "Human's Heaven" refers to the Heaven that completes my form, arising from being and governed by myself. Birth comes first, completion follows later; thus, the meaning of Pre-Heaven (Xiantian) and Post-Heaven (Houtian) becomes clear. Therefore, speaking from the perspective of innate endowment, those with strong Pre-Heaven endowments tend to live long, while those with weak Pre-Heaven endowments tend to die young. Those who cultivate their Post-Heaven aspect well will extend their longevity further, while those who deplete their Post-Heaven aspect will shorten their lives even more.
Regarding the body, bones belong to Pre-Heaven, while muscles belong to Post-Heaven. Spirit (Shen) belongs to Pre-Heaven, while appearance belongs to Post-Heaven. Complexion can be discerned: those with a vigorous hue live long, while those with an artificial or flashy hue die young. A complexion that is tender yet retains vigor is auspicious, whereas one that is vigorous yet appears tender is inauspicious. Voice can be discerned: those with full and resonant voices live long, while those with timid and short voices die young. Even if the voice is fine, if it is long-lasting, it is auspicious; even if the voice is loud, if it is hurried, it is inauspicious. Physical form can be discerned: those who are firm live long, while those who are brittle die young. Even if the body is emaciated, if movements are enduring, it is auspicious; even if the physique is robust, if spirit easily becomes fatigued, it is inauspicious. Activity and stillness can be discerned: those who are still live long, while those who are restless die young. Although temperament may seem urgent, if there is harmony within the urgency, it is auspicious; although Yang Qi may seem strong, if Yin Essence is thin within, it is inauspicious. Regarding age and growth, although initially weak, if one gradually grows stronger, it is a sign of late blooming. Regarding temperament, if youth is showy and prone to arrogance, it is a sign of early decay. Therefore, those who possess both Pre-Heaven and Post-Heaven fully will undoubtedly enjoy old age. Those who lose control over both Pre-Heaven and Post-Heaven will surely suffer premature death, which needs no divination to know.
Speaking from the perspective of human agency, one should not rely on strong Pre-Heaven endowments; reliance leads to the loss of that strength. One must be cautious regarding weak Post-Heaven conditions; caution allows humans to overcome fate. What does caution entail? Being cautious with emotions preserves Heart-Shen (Spirit); being cautious with cold and heat preserves Lung-Qi (Defensive Qi); being cautious with alcohol and lust preserves Liver and Kidney; being cautious with fatigue and diet preserves Spleen and Stomach. Only joy can nurture life, and nothing promotes joy better than doing good. Only fortune can preserve life, and those seeking fortune must never deceive Heaven. As long as the interior and exterior remain intact, how can pathogenic factors invade? Thus, the power over Pre-Heaven and Post-Heaven lies within us. Therefore, Guangchengzi said: "Do not exhaust your form, do not agitate your Jing (Essence), and you may attain long life." How profound! These two words encompass the essence completely. Do not consider this easy and neglect it.