Shu'ayb is chosen by Allah to be a prophet to the people of Madyan, who were deeply involved in fraudulent trade practices and idol worship.
Shu'ayb's message to them is clear: abandon their dishonesty and turn back to the worship of the one true God, Allah.
However, the people of Madyan persist in their wickedness and unjust dealings.
As a consequence, Allah sends a calamity, often interpreted as an earthquake, which devastates them, leaving the land desolate.
Shu'ayb and the few who believed in his message are spared as a testament to Allah's justice.