It is narrated by Hazrat Abu Saeed RA that a Muslim once said to the Prophet, PBUH “What rewards do we get for our illnesses?” The Prophet Muhammad PBUH said that it is the atonement of your sins.  HazratAbi Bin Kaab RA was also present in that gathering. He asked what if the illness is very little. The Prophet PBUH said that even if only a thorn has pricked, or even anything smaller. [Masand Ahmad]. HazratUmmulAla narrates that the Prophet Muhammad PBUH visited me while I was ill. He congratulated me that illness cleans off a Muslim’s sins just like fire cleans off the stains of iron and silver. [Abu Dawood]. HazratJaabir Bin Abdullah RA narrates that when a believer men/women or Muslim men/Muslim women falls ill, then Allah sheds his sin due to his illness. Another narration is that Allah expiates their sins. [Masand Ahmad]. Hazrat Ayesha RA narrates that Prophet Muhammad said that when a true believer falls ill, Allah frees him from sins similar to how a furnace cleans the dirt of iron. [IbnHayan]. HazratAnas RA narrates that Prophet Muhammad PBUH said that when a person falls ill for three days, then he is purified from sins as if he was born today. [Tibrani]