Su Qin was a native of Luoyang during the Warring States Period. He had sought to become an adviser to the rulers of several states, but without success. Returning home in low spirits, he found that his parents treated him coldly, as if he were not their son; his wife sat at the loom and did not rise to greet him; and even his sister-in-law would not prepare meals for him. Mortified, Su Qin shut himself up in his room and devoted himself to his books. After a year he went traveling in search of employment again. This time, he managed to persuade the rulers of six states to form an alliance against the powerful and aggressive State of Qin. He himself was made prime minister of the alliance. Wearing the regalia of the prime minister of all the six states, Su Qin returned home with all the pomp and circumstance befitting his high rank. Hearing of his approach, his parents cleaned the house, rebuilt the local road, prepared wine and exotic dishes, and went out thirty li from the city to greet him with music. His wife dared not look him in the face. His sister-in-law crawled on all fours and kowtowed to him again and again to apologize for her former offence. Su Qin smiled and asked her, “Why were you so arrogant before and so humble now?” She answered, “It is because you hold a high position and have great wealth now.” Su Qin sighed and said, “I am the same person as I was before. Now that I am rich and hold a high position, all my kin are in awe of me. But when I was poor and humble, they slighted me. If even my own kith and kin behave like this, how can I expect others to behave?”
Later, the phrase “haughty before and reverent afterwards” came to be used to indicate how people’s attitudes toward one can easily change, depending on one’s change of fortune.
Source: The Stories Behind 100 Chinese Idioms by He Zeren & Zhou Lingzhong