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." (Using translation from Bukhārī 5662)   

أَنَّ رَسُولَ اللهِ ﷺ دَخَلَ عَلَى أَعْرَابِيٍّ يَعُودُهُ فَقَالَ «لَا بَأْسَ عَلَيْكَ طَهُورًا إِنْ شَاءَ اللهُ» فَقَالَ بَلْ هِيَ حُمَّى تَفُورُ فِي عِظَامِ شَيْخٍ كَيْمَا تُزِيرُهُ الْقُبُورَ قَالَ النَّبِيُّ ﷺ «فَنِعْمَ إِذًا»