Volume 9 · Book 93 · Hadith 589
Narrated Abu Huraira: the Prophet said, "Allah said, "I have prepared for My righteous slaves (such excellent things) as no eye has ever seen, nor an ear has ever heard nor a human heart can ever think of.' "
— Sahih Bukhari, Volume 9, Book 93: Oneness, Uniqueness of Allah (Tawheed), Hadith #589