It is narrated from Sayyiduna Sahl bin Sa'd (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him), describing Paradise, said: "In it is what no eye has seen, no ear has heard, and has never occurred to the heart of any human being."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5979