Prophet Syu'aib was sent to the people of Madyan — a strategic trading city on the route between Hijaz and Syam. They were wealthy from trade, but loved to cheat: shortchanging measures and weights, deceiving customers, robbing travelers.
Syu'aib said: "Give full measure and weight with justice. Do not deprive people of their rights." (Hud: 85). He also called them to worship Allah alone.
They mocked: "Does your prayer command you to teach us to leave what our forefathers worshipped, or to forbid us from doing what we want with our wealth?"
Syu'aib remained patient. He said: "I don't wish to differ from you in what I forbid you from. I only want reform within my capacity."
They kept refusing. Eventually Allah sent a terrible earthquake. Madyan was destroyed overnight. Only Syu'aib and his followers survived.
For his eloquence and patience in preaching, Syu'aib earned the title "Khatib al-Anbiya" — Preacher of the Prophets.
For children: honesty in the smallest transactions — change, weights, promises, queues — is worship.