Dua 1
لَا بَأْسَ طَهُوْرٌ اِنْ شَآءَ اللّٰهُ
No harm; if Allah wills, this illness is a purification (from sins).
Sahih al-Bukhari, no. (3616).
Supplications for the sick when visiting them
Dua 2
Recite the following words seven times:
اَسْاَلُ اللّٰهَ الْعَظِيْمَ رَبَّ الْعَرْشِ الْعَظِيْمِ اَنْ يَّشْفِيَكَ
I ask Allah the Magnificent, Lord of the Mighty Throne, to cure you.
Sahih Sunan Abi Dawud, no. (3106), Sunan at-Tirmidhi, no. (2083), and al-Albani graded it Sahih in “Sahih Sunan Abi Dawud” (8/423) no. (2719).
This hadith states the virtue of this supplication: whoever says it beside a sick person whose time of death has not yet come, Allah will cure him.