From Sahih Bukhari (Hadith 5662):
Narrated Ibn `Abbas:Allah's Messenger (ﷺ) entered upon sick man to pay him a visit, and said to him, "Don't worry, Allah willing, (your sickness will be) an expiation for your sins." The man said, "No, it is but a fever that is boiling within an old man and will send him to his grave." On that, the Prophet (ﷺ) said, "Then yes, it is so
Reference: Bukhari 5662