Prophet - messenger Shu'aib(peace be upon him) was sent to the people of Madyan. These people, who were merchants and traders. Shu'aib (peace be upon him) said to them: You should pay heed to laws of Allah Almighty who has created you. You should not cheat other people who come to buy from you. But the did not listen to messenger. They wanted to make more money, and they earned more by cheating their customers. So they went on doing it. What was more, they refused to believe what prophet told them. Get out of our town or we will throw stones at you.
It did not take long for God Alimghty punishment to come to them. They all died in one day from a terrible earthquake. The large amounts of money which they had gained and collected could not help them at all. So their dishonest was punished and it had done them no good at all to demand high prices and get rich quickly.
Allah Almighty exposed the story of Shu'aib (pbuh): "To the people of Madyan (Madian) (We sent) their brother Shu'aib. He said: "O my people! Surrender your will to Allah Almighty , you have no other Ilah (God) but Him. Verily! a obvious evidence (sign) from your nourisher has come unto you; so give full measure and full weight and wrong not men in their things, and do not mischief on the earth after it has been set in order that will be better for you, if you are faithful. And sit not on every road, intimidating, and hindering from the Path of God Almighty those who believe in, and looking for to make it twisted. Remember when you were but few, and He multiplied you. See what was the end of the Mufsideen (mischief makers, corrupts and liars). And if there is a party of you who believes in that which I have been sent and a party who do not believe, so be patient until Allah Almighty judges between us, and God Almighty is the best of judges."
The chiefs of those who were egotistical among his people said: "We shall certainly drive you out, O Shu'aib! and those who have believed with you from our town, or else you all shall return to our religion." The prophet-messenger said that In Allah Almighty we put our trust. Our creator! judge between us and our people in truth, for You are the Best of those Who gives judgment."
The chiefs of those who disbelieved among his people said to their people: "If you follow Shu'aib be sure then you will be the losers!" Then he (shu'aib) turned from them and said: "O my people! I have indeed conveyed my Lord's Messages unto you and I have given you good advice. Then how can I sorrow for the disbelieving people's (destruction)." (7:85-93 Quran)
The people of Madyan were Arabs who lived in the country of Ma'an, part of which today is greater Syria . They were a avaricious people who did not believe that Allah Almighty existed and who led wicked lives. They gave short measure, praised their goods beyond their worth, and hid their defects. They lied to their customers, thereby cheating them.