Sahih Muslim Book 40, Hadith Number 6780.

Abu Huraira reported Allah’s Apostle (may peace be upon him) as saying that: Allah the Exalted and Glorious, said: I have prepared for My pious servants which no eye has ever seen, and no ear has ever heard, and no human heart has ever perceived but it is testified by the Book of Allah. He then recited: “No soul knows what comfort has been concealed from them, as a reward for what they did”. (xxxii.17)