During the Spring and Autumn Period (春秋 chūn qiū,770-476 BC),there was a high official in the State of Jin (jìn guó 晋国). He once saw a farmer working in the field and his wife bringing his lunch to him in a very respectful manner. He showed great interest in the matter. He took the farmer back to Jin with him,and said to the King of Jin, "Respect is a demonstration of virtue. If one is respectful,he must be virtuous. We should educate our people with virtue." But the King asked, "His father is guilty, is it wise to do so?" He replied, "Guan Zhong (guǎn zhòng 管仲) had been enemy to the Duke Huan of Qi (qí wáng 齐王), but the duke appointed Guan Zhong prime minis ter and finally accomplished his hegemony. Shun (shùn 舜) exiled Gun (gǔn 鲧) but promoted his son Yu (yǔ 禹). You just make use of his strong points."  At last, the ruler of Jin took his advice and put the farmer in an important position.

Later, this idiom means a couple treats each other with respect like guests.

春秋时期，晋国有个大官。有一次他外出，看见一个农夫在田里干活，他的妻子很恭敬地给他端上午饭。夫妻之间就象客人一样，非常客气。他很感动。他把这个农夫带到晋王的面前，要求晋王给他封官。他对晋王说：“互相尊重是一种美德。一个品德高尚的人才会待人有礼貌。我们应该培养我们臣民养成这种美德。”晋王说道：“他的父亲是个罪人，我们用他合适吗？”他答道：“管仲曾是齐王的敌人，但齐王后来让他做了齐国的相国，帮助他完成了霸业。当年舜放逐了鲧却重用了鲧的儿子禹。你只要利用他的长处就可以了。”最后，晋王听从了他的话，重用了这个农夫。
后来，人们用“相敬如宾”来表示夫妻之间互相尊重，好象客人一般。

相敬如宾 (xiāng jìng rú bīn)
【翻译】Treat each other with respect.
【释义】形容夫妻互相尊敬，像对待宾客一样。
【例句】他们结婚了这么多年还能相敬如宾，真的很不容易啊！
【近义词】相亲相爱、举案齐眉、心心相印
【反义词】琴瑟不调、敬而远之、同床异梦