Sahih Muslim Book 45, Hadith 65
I heard Allah's Messenger (ﷺ) as saying: There is nothing (in the form of trouble) that comes to a believer even if it is the pricking of a thorn that there is decreed for him by Allah good or his sins are obliterated.
No trouble comes to a believer even if it is the pricking of a thorn that it becomes (the means) whereby his sins are effaced or his sins are obliterated. Yazid says: He does not know which word 'Urwa said (whether he said Qussa or Kuffira).
Never a believer is stricken with discomfort, hardship or illness, grief or even with mental worry that his sins are not expiated for him.