Indeed, Qaroon was among the people of Moses, but he became tyrant upon them; and We gave him of treasures, indeed the keys of it was a burden to bear for a group of strong men; when his people said to him: "You do not exult, indeed Lord Allah doesn’t like the exultant”.
Qaroon was a rich man from the children of Israel. He exulted upon his abundant wealth by forgetting the Lord. It is told in verses 84: 10-13: “For the one who is given his Recording Book behind his back, he will cry out for destruction and he will be roasted in the Blaze. Indeed, he had been exalted among his family”. The believer is commanded to say such exulting Fujjar in this world as: “You enjoy here a little, indeed your return is into the Hell” as explained in verses 9: 81-82. It is explained in verse 10: 58 that one can be exulted only with Adhikr which is the Bounty and Mercy. See explanation 16: 90; 23: 51-53 and 25: 33-34.