Riyad as-Salihin

Abu Sa'id and Abu Hurairah (May Allah be pleased with him) reported that the Prophet (ﷺ) said: "Never a believer is stricken with a discomfort, an illness, an anxiety, a grief or mental worry or even the pricking of a thorn but Allah will expiate his sins on account of his patience".

[Al-Bukhari and Muslim].