Musnad Ahmad 1034:199

Yazid narrated to us, Abu Malik informed us, from Rib'i ibn Hirash, from Hudhayfah, that he arrived from [the presence of] Umar. He said: When we sat with him yesterday, he asked the companions of the Prophet, peace and blessings of Allah be upon him: "Which of you heard the statement of the Messenger of Allah, peace and blessings of Allah be upon him, regarding the tribulations (fitan)?" They said: "We heard it." He said: "Perhaps you mean the tribulation of a man regarding his family and his wealth?" They said: "Yes." He said: "I am not asking about that; that is expiated by prayer, fasting, and charity. But which of you heard the statement of the Messenger of Allah, peace and blessings of Allah be upon him, regarding the tribulations that surge like the surging of the sea?" He said: The people remained silent, and I thought he meant me. He said: I said: "I." He said: "You? May your father be for Allah!" He said: I said: "Tribulations are presented to the hearts, [layer by layer] like a reed mat. Any heart that rejects them, a white dot is marked in it; and any heart that absorbs them, a black dot is marked in it, until the hearts become two types: white like a smooth stone, which no tribulation will harm as long as the heavens and the earth exist; and the other, black and dusty, like an overturned cup, [and he tilted his palm], not recognizing any good nor rejecting any evil, except for what it has absorbed of its own desire." And I told him that between it and them is a closed door, which is about to be broken, a breaking. Umar said: "A breaking, may you have no father?" I said: "Yes." He said: "If it were opened, perhaps it could be returned and closed?" I said: "No, rather a breaking." He said: And I told him that that door is a man who will be killed or die—a narration that is not a mistake.