Sahih Muslim Book 032, Hadith Number 6245.
Chapter : Whenever a believer falls sick or is stricken with grief or something tike it, there is a reward for him even if it is pricking of a thorn.
'Ata' b. Abi Rabih said: Ibn Abbas said to me: May I show you a woman of Paradise? I said: Yes. He said: Here is this dark-complexioned woman. She came to Allah's Apostle (may peace be upon him) and said: I am suffering from falling sickness and I become naked; supplicate Allah for me, whereupon he (the Holy Prophet) said: Show endurance as you can do and there would be Paradise for you and, if you desire, I supplicate Allah that He may cure you. She said: I am prepared to show endurance (but the unbearable trouble is) that I become naked, so supplicate Allah that He should not let me become naked, so he supplicated for her.