The Thamud were descendants of the surviving 'Ad. They lived in rocky valleys and were masters at carving homes into stone cliffs. Allah gave them strength, but they too began worshipping idols.
Allah sent Prophet Salih, one of their own. He invited them back to tawhid. They said: "Give us proof. Bring out a live she-camel from that rock!"
Prophet Salih prayed to Allah, and a great she-camel emerged from the stone. Allah said: "This camel is a sign. Let her drink from the well one day, you another. Don't harm her, or punishment will come."
Some believed. But nine wicked men from Thamud plotted to kill the camel. They succeeded. Then they approached Prophet Salih to kill him too, but Allah protected the Prophet.
After three days, Allah sent a tremendous thunderclap — all the disbelievers of Thamud died instantly. Only Prophet Salih and his followers survived.
For children: sometimes Allah gives very clear signs. Those who deny don't deny because they don't know — but because they don't want to.