be haughty at first but respectful later

This idiom comes from Intrigues of the Warring States·Intrigues of Qin I. During the Spring and Autumn Period and the Warring States Period,there was afamous Political Strategist named Su Qin. He and Zhang Yi had learned the political strategy from Guiguzi.

Before Su Qin's success, he went out preaching, accomplishing nothing at all. So every time he returned home, he was treated coldly by his family and county people.They all considered him goodfor nothing. Especially his sister-in-law pointed out that he idled about and did no decent work every day, and also said he could never hold up his head in future.

Since then Su Qin studied very hard from morning till night. Even tieing his hair to a beam to keep from nodding, or proding himself awake with an awl in the thigh, he studied assiduously. Finally he achieved great success in bringing the six states together to resist the strong State of Qin.

He was offered prime minister by Duke Wen of Yan and also to be Marquis Wuan by Duke of Zhao. Once on his way to the State of Chu, when he passed through his native town--Luoyang, his parents welcomed him at the countryside and his sister-in-law got down on her knees and asked for forgiveness. Then Su asked:"Why are you so arrogant before but respectful now." She was ashamed and said : "Because now you are not only in high post but also rich." Hearing this, Su left a deep sigh and said: "Why do all the common people treat others only by their position and wealth?"

Now we use it to describe that some snobs adopt different manners towards the other's failure or success.

此語出自《戰(zhàn)國策·秦策一》。春秋戰(zhàn)國時代，有位著名的縱橫家叫蘇秦。他曾和張儀一起拜鬼谷子為師，學習“縱橫之術”。

當蘇秦尚未成名之時，他外出游說，一事無成。每次他窮困潦倒地回到家中，都受到眾人的冷落，被認為沒有出息。特別是他的嫂子罵他游手好閑，不務正業(yè)，斷言他永無出頭之日。

為此蘇秦發(fā)憤讀書，甚至“懸梁刺股”地刻苦讀書。學成后他又外出游說，終于游說六國成功，一起對付強大的秦國。

他被燕文公拜為相國，又被趙肅侯封為武安君，掛相印。他在去楚國的路上，路過洛陽，他父母特地到洛陽郊外迎接他，他的嫂子卻伏地長跪不起向他請罪。蘇秦見了問她：“嫂嫂，你為什么從前那么傲慢，而今天卻這樣卑恭呢?”他嫂子又愧又怕地說：“那是因為小叔現在職位高，金錢多??！”蘇秦聽了，長嘆一聲地說：“人世間，不以貧賤富貴來待人的人實在太少了！”

后用此典諷刺那些勢利小人先是傲慢待人，見人成功后又恭敬，前后態(tài)度不一樣。