Shu'ayb (peace be upon him) was sent to the people of Madyan, saying, "O my people, worship Allah; you have no deity other than Him" (7:85). Beyond idolatry, his people were guilty of cheating in trade, so he urged them to give full measure and weight and not to deprive people of their due or spread corruption in the land (7:85, 11:84-85).
He reminded them that what remains lawful from Allah is better for them, and that he was not a guardian over them but a sincere adviser (11:86-88). The chiefs mocked him, questioning whether his prayer commanded him to make them abandon their fathers' ways and their freedom to do as they pleased with their wealth (11:87).
They threatened to stone him and drive him and the believers out unless they returned to their ways, but Shu'ayb held firm and placed his trust in Allah (7:88-89, 11:91). When they persisted in denial, the punishment came: they were seized by a mighty blast and an overshadowing gloom, and by morning they lay lifeless in their homes (7:91, 11:94, 26:189).
Allah saved Shu'ayb and those who believed with him by His mercy, and Madyan became a lesson for those who reflect on justice and honesty (11:94-95).