Jami' at-Tirmidhi 2086

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 ‏"‏ ‏.‏

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

Reference

Jami' at-Tirmidhi 2086

In-book

Book 28, Hadith 51