Messenger of Allah 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."
أَنَّ رَسُولَ اللَّهِ ﷺ دَخَلَ عَلَى رَجُلٍ يَعُودُهُ فَقَالَ لاَ بَأْسَ طَهُورٌ إِنْ شَاءَ اللَّهُ فَقَالَ كَلاَّ بَلْ حُمَّى تَفُورُ عَلَى شَيْخٍ كَبِيرٍ كَيْمَا تُزِيرَهُ الْقُبُورَ قَالَ النَّبِيُّ ﷺ فَنَعَمْ إِذًا