Sahih Muslim Book 032, Hadith Number 6237.
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.
Aswad reported that some young men from the Quraish visited 'Aisha as she was in Mina and they were laughing. She said: What makes you laugh? They said: Such and such person stumbled against the rope of the tent and he was about to break his neck or lose his eyes. She said: Don't laugh for I heard Allah's Messenger (may peace be upon him) as saying: If a Muslim runs a thorn or (gets into trouble) severe than this, there is assured for him (a higher) rank and his sins are obliterated.