Musnad Ahmad 30:1269

Hassan ibn Musa narrated to us, Zuhair narrated to us, from Suhayl, from his father, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The Euphrates will uncover a mountain of gold," or: "The Hour will not be established until the Euphrates uncovers a mountain of gold, so people will fight over it, and out of every hundred, ninety-nine will be killed." "O my son, if you reach it, then do not be among those who fight over it."