《礼记·乐记》
在天上有日月星辰风雷等不同现象，在地上有山川草木鸟兽等不同形态，礼就是这样体现着天地之间的各种区别。
在天成象，在地成形；如此，则礼者天地之别也。
In Heaven, there are different phenomena such as the sun, moon, stars, wind and thunder; on Earth, there are different forms such as mountains, rivers, plants, birds and animals. Ritual thus embodies the various distinctions between Heaven and Earth.