Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: "It is written in the Torah: For those whose sides forsake their beds there is what no eye has seen, no ear has heard, and has never occurred to the heart of any human being. And the same is in the Qur'an: 'No soul knows what has been hidden for them of the coolness of the eyes' [Surah al-Sajdah: 17]."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9007