Musannaf Ibn Abi Shayba 37:516

Al-Fadl ibn Dukayn narrated to us, he said: Abd al-Salam al-Sulami narrated to us, he said: Wabara narrated to me, from Mujahid, who said: You will not see the relief until four men rule, all of them from the loins of one man. If that happens, then perhaps.