Quran 7: 187-188, which mean:
[Some of Quraish tribesmen said to the Prophet – salam to him: "If you are a prophet, tell us when we will die!"
Therefore, this aya was revealed:]
(187. They question you [Mohammed] of the Hour [of their death], when its settlement be?
Say: "The knowledge about the [hour of your death] is [exclusively] with my Lord [alone]; none but He will manifest it with its [due] time;
it has been so tremendous in the heavens and the earth;
only, all of a sudden it will come to you."
They ask you as if you are unaware about it.
Say: "The knowledge about it is [exclusively] with God [alone], but most of people know not [about the truth.]"
[When they asked the Prophet about the 'unknown fore-future', His saying – be glorified – in the Quran was revealed:]
188. Say [Mohammed, to them]: "For myself, I cannot bring any profit, nor avert any hurt, but only that which God wills.
Had I had the knowledge of the fore-future, I should have had abundance of wealth, and adversity would not have touched me.
I am only a warner [against idolatry], and a bearer of good tidings [of Paradise and prosperity] to a people believing [in God and His messenger.])
More explanation of these two grat ayat is in the link: