What to say to someone who is ill

'A'isha (ra) said, "When the Messenger of Allah ﷺ came to Madina, Abu Bakr (ra) and Bilal (ra) came down with a fever. I visited them and asked, 'Father, how are you? Bilal, how are you?' When Abu Bakr's (ra) fever worsened, he said:
"Every body is given the prayer to arise healthy among his people, yet death is nearer to him than his shoe-laces." And whenever Bilal’s (ra) fever subsided, he would recite, "Would that I know that I will ever spend a night in a valley surrounded by Izkhir and Jaleel (two kinds of sweet smelling grass). And that I will arrive one day to the waters of Majannah and observe (the mountains) Shamah and Tafeel" Ayshah (ra) went to the Prophet M, and informed him of what transpired with these two men. Thereupon, he made this supplication: "O Allah, make us love Madinah as dearly as we love Makkah, or more than that. O Allah! Make it healthy for us and bless for us it sa' and mudd. And remove its fever putting it in al-Juhfah"

حَدَّثَنَا إِسْمَاعِيلُ بْنُ أَبِي أُوَيْسٍ قَالَ: حَدَّثَنِي مَالِكٌ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ أَنَّهَا قَالَتْ: لَمَّا قَدِمَ رَسُولُ اللهِ ﷺ الْمَدِينَةَ وُعِكَ أَبُو بَكْرٍ وَبِلاَلٌ، قَالَتْ: فَدَخَلْتُ عَلَيْهِمَا، قُلْتُ: يَا أَبَتَاهُ، كَيْفَ تَجِدُكَ؟ وَيَا بِلاَلُ، كَيْفَ تَجِدُكَ؟ قَالَ: وَكَانَ أَبُو بَكْرٍ إِذَا أَخَذَتْهُ الْحُمَّى يَقُولُ:
كُلُّ امْرِئٍ مُصَبَّحٌ في أهْلِهِ... والمَوْتُ أدْنَى مِن شِرَاكِ نَعْلِهِ
وَكانَ بلَالٌ إذَا أُقْلِعَ عنْه يَرْفَعُ عَقِيرَتَهُ فيَقولُ:
أَلَا لَيْتَ شِعْرِي هلْ أبِيتَنَّ لَيْلَةً... بوَادٍ وحَوْلِي إذْخِرٌ وجَلِيلُ
وَهلْ أرِدَنْ يَوْمًا مِيَاهَ مِجَنَّةٍ... وهلْ تَبْدُوَنْ لي شَامَةٌ وطَفِيلُ
قَالَ: قَالَتْ عَائِشَةُ: فَجِئْتُ رَسولَ اللَّهِ صَلَّى اللهُ عليه وسلَّمَ فأخْبَرْتُهُ، فَقَالَ: اللَّهُمَّ حَبِّبْ إلَيْنَا المَدِينَةَ كَحُبِّنَا مَكَّةَ أوْ أشَدَّ، وصَحِّحْهَا، وبَارِكْ لَنَا في صَاعِهَا ومُدِّهَا، وانْقُلْ حُمَّاهَا فَاجْعَلْهَا بالجُحْفَةِ.

Ibn 'Abbas reported that the Prophet ﷺ went to visit a bedouin who was ill. When the Prophet ﷺ 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 ﷺ said, "Then yes (it is)".

حَدَّثَنَا مُعَلَّى، قَالَ: حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ الْمُخْتَارِ، قَالَ: حَدَّثَنَا خَالِدٌ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، أَنَّ النَّبِيَّ ﷺ دَخَلَ عَلَى أَعْرَابِيٍّ يَعُودُهُ، قَالَ: وَكَانَ النَّبِيُّ ﷺ 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 ﷺ: فَنَعَمْ إِذًا.