Sahih Muslim Book 45, Hadith 67
"Whoever does evil will be requited for it", and when this was conveyed to the Muslims they were greatly perturbed. Thereupon Allah's Messenger (ﷺ) said: Be moderate and stand firm in trouble that falls to the lot of a Muslim (as that) is an expiation for him; even stumbling on the path or the pricking of a thorn (are an expiation for him). Muslim said that 'Umar b. Abd al-Rahman Muhaisin was from amongst the people of Mecca.
Never a believer is stricken with discomfort, hardship or illness, grief or even with mental worry that his sins are not expiated for him.
Umm Sa'ib or Umm Musayyib. why is it that you are shivering? She said:" It is fever and may it not be blessed by Allah, whereupon he (the Holy Prophet) said: Don't curse fever for it expiates the sin of the children of Adam just as furnace removes the alloy of iron.