As-Sajdah 32:17

Fala taAAlamu nafsun maokhfiya lahum min qurrati aAAyunin jazaan bima kanooyaAAmaloon

And no soul knows what has been hidden for them of comfort for eyes [i.e., satisfaction] as reward for what they used to do.

So, no one knows the delight of eyes that has been reserved for them in secret, as a reward of what they used to do.