The saying 'courtesy calls for a return' comes from the Quli chapter of the Book of Rites.
Tips
history
Here 曲 means 'detailed, in every particular': the chapter sets out the small rules of conduct, how to sit, eat, greet elders and mourn, and is so long that it is split into two parts, 曲礼上 and 曲礼下. It opens 毋不敬 'let nothing be done without respect'.
culture
Many sayings start here: 礼尚往来; 刑不上大夫 'punishments do not reach up to the high officials'; the duty to avenge a father, whose killer one may not live with under the same sky, the source of 不共戴天; and 弱冠 for a man of twenty, the age at which he was capped.
