It is narrated from Sayyiduna Ubayy bin Ka'b al-Ansari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The Hour will not be established until the Euphrates uncovers a mountain of gold, and nine out of every ten of them will fight and be killed (to obtain it)."
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 534