Full Sharh — Al-Adab Al-Mufrad 528
حَدَّثَنَا مُعَلَّى، قَالَ: حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ الْمُخْتَارِ، قَالَ: حَدَّثَنَا خَالِدٌ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، أَنَّ النَّبِيَّ صلى الله عليه وسلم دَخَلَ عَلَى أَعْرَابِيٍّ يَعُودُهُ، قَالَ: وَكَانَ النَّبِيُّ صلى الله عليه وسلم إِذَا دَخَلَ عَلَى مَرِيضٍ يَعُودُهُ قَالَ: لاَ بَأْسَ طَهُورٌ إِنْ شَاءَ اللَّهُ، قَالَ: ذَاكَ طَهُورٌ، كَلاَّ بَلْ هِيَ حُمَّى تَفُورُ، أَوْ تَثُورُ، عَلَى شَيْخٍ كَبِيرٍ، تُزِيرُهُ الْقُبُورَ، قَالَ النَّبِيُّ صلى الله عليه وسلم: فَنَعَمْ إِذًا.
English Translation
Ibn 'Abbas reported that the Prophet, may Allah bless him and grant him peace, went to visit a bedouin who was ill. When the Prophet, may Allah bless him and grant him peace, visited someone who was ill, he would say, 'There is no harm in it. It is a purification, Allah willing." That man then said, "A purification! No, rather it is a fever which boils (or appears) in an old man and will cause him to visit the graces." The Prophet, may Allah bless him and grant him peace, said, "Then yes (it is)".
Source
Al-Adab Al-Mufrad(الأدب المفرد)
Visiting the Ill
Hadith Number
528