Sahih al-Bukhari 75:22
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
Sahih al-Bukhari 75:22
In-book reference
Book 75, Hadith 22
Arabic Text
حَدَّثَنَا إِسْحَاقُ، حَدَّثَنَا خَالِدُ بْنُ عَبْدِ اللَّهِ، عَنْ خَالِدٍ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ ـ رضى الله عنهما ـ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم دَخَلَ عَلَى رَجُلٍ يَعُودُهُ فَقَالَ " لاَ بَأْسَ طَهُورٌ إِنْ شَاءَ اللَّهُ ". فَقَالَ كَلاَّ بَلْ حُمَّى تَفُورُ عَلَى شَيْخٍ كَبِيرٍ كَيْمَا تُزِيرَهُ الْقُبُورَ. قَالَ النَّبِيُّ صلى الله عليه وسلم " فَنَعَمْ إِذًا ".