From Sahih Bukhari (Hadith 4779):
Narrated Abu Huraira:Allah's Messenger (ﷺ) said, "Allah said, 'I have prepared for my pious worshipers such things as no eye has ever seen, no ear has ever heard of, and nobody has ever thought of." Abu Huraira added: If you wish you can read:-- 'No soul knows what is kept hidden (in reserve) for them of joy as reward for what they used to do
Reference: Bukhari 4779