ENOfficial
Anas bin Malik narrated that the Messenger of Allah (S.A.W) said: "The parable of the ill when he is cured and becomes healthy is that of hail that falls from the heavens in its purity and its color."
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا عَلِيُّ بْنُ حُجْرٍ، قَالَ أَخْبَرَنَا الْوَلِيدُ بْنُ مُحَمَّدٍ الْمُوَقَّرِيُّ، عَنِ الزُّهْرِيِّ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِنَّمَا مَثَلُ الْمَرِيضِ إِذَا بَرَأَ وَصَحَّ كَالْبَرْدَةِ تَقَعُ مِنَ السَّمَاءِ فِي صَفَائِهَا وَلَوْنِهَا " .
sunnah.com