Kitab al-Fitan · Nu'aym ibn Hammad

The fourth trial lasts eighteen years, then it clears up when it clears, and the Euphrates has receded, creating a mountain of gold upon which the nation will fall, and seven out of every nine will be killed.

It was narrated from Abu Hurairah that the Messenger of Allah (ﷺ) said:“The Hour will not begin until the Euphrates uncovers a mountain of gold and people fight over it, and out of every ten, nine will be killed.’”