The Hour is like a woman in the last stage of pregnancy, whose family do not know when she will suddenly deliver

It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that on the night when the Messenger of Allah (peace and blessings be upon him) was taken on the Night Journey (Mi'raj), he (peace and blessings be upon him) met Ibrahim, Musa and Isa (peace be upon them). They began to discuss the Hour and asked Ibrahim (peace be upon him) about it, but he had no knowledge of (its time). Then they asked Musa (peace be upon him), and he too had no knowledge of it. Then the matter was referred to Isa (peace be upon him), and he said: "Allah Almighty has informed me about the events that will take place before it, other than the time of the establishment of the Hour; as for the exact time of its occurrence, no one knows it except Allah, the Mighty and Majestic." Then he mentioned the emergence of the Dajjal and said: "So I will descend (from the sky) and kill him. Then the people will return to their lands, and they will be confronted by Gog and Magog, who will come rushing down from every elevation. They will drink up every water they pass by and ruin everything they pass by. So the people will (in distress) cry out to me for help, and I will supplicate to Allah, and He will send down water from the sky which will carry away their corpses and cast them into the sea. Then the mountains will be crushed to dust, and the earth will be spread out like leather. And Allah has promised me that when all this has happened, the Hour will be for the people like a pregnant woman whose term is complete, whose family do not know when she will suddenly give birth, by night or by day." The narrator al-Awwam says: I found confirmation of this in the Book of Allah, the Mighty and Majestic. Then he recited this verse: "Until, when Gog and Magog are let loose and they rush down from every elevation, and the true promise draws near." [Surah al-Anbiya': 96 - 97]

It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The signs (of the Hour) are like beads strung on a thread; when the thread breaks, they will begin to appear (rapidly) one after another."
This hadith is sahih (authentic) on the condition of Imam Muslim, but the two Shaykhs (Bukhari and Muslim) did not record it.

It is narrated from Sayyiduna Hudhayfah (may Allah be pleased with him) that he went out to the outskirts of Kufah, and a man was with him. He looked towards the Euphrates and said to his companion: "What will be your state when you see them coming out, or being driven out, from there, and they will not taste even a single drop of its (the Euphrates') water?" A man asked: O Abu Abdullah! Is that what you think? He said: "It is not what I think; rather, I know it (with certainty)."
This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it.

It is narrated from Abu Thawr that he said: I was sitting with Sayyiduna Hudhayfah and Sayyiduna Abu Mas'ud (may Allah be pleased with them both) at the time when the people of Kufah turned back Sa'id bin al-As on the Day of al-Jara'ah. Abu Mas'ud said: I did not think that he (Sa'id) would go back without blood being shed. At this Hudhayfah said: But by Allah, I knew that we would return in this way and that not even the amount of blood in a cupping vessel would be shed in this matter. And I had no knowledge of anything about this except what I learned during the lifetime of the Prophet (peace and blessings be upon him): "A man will be a believer in the morning and by evening he will have become a disbeliever, with nothing of his religion left with him; and he will be a believer in the evening and by morning he will have nothing of his religion left with him. He will fight in today's tribulation and Allah, the Mighty and Majestic, will destroy him tomorrow. His heart will be turned upside down and his lower part will come on top." I asked: His lower part? He said: "Yes, his rear (that is, he will be disgraced and humiliated)."

It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) concerning this verse: "And when the word is fulfilled against them, We will bring forth for them a beast from the earth that will speak to them" [Surah al-Naml: 82], that he said: "(This will happen) when people no longer enjoin good and no longer forbid evil."