Surah Taha 20:22

وَٱضْمُمْ يَدَكَ إِلَىٰ جَنَاحِكَ تَخْرُجْ بَيْضَآءَ مِنْ غَيْرِ سُوٓءٍ ءَايَةً أُخْرَىٰ

And draw in your hand to your side; it will come out white without disease - another sign,

Translation: Saheeh International

Tafsir

And thrust your hand the right one meaning the palm into your flank — that is your left side below the arm into the armpit and then take it out — it will emerge white in contrast to the skin-colour that it was without any fault that is without any sign of leprosy radiating like the rays of the sun blinding to the eyes …

Excerpt from Tafsir al-Jalalayn, commentary on 20:22, via Quran.com. The reader has the full commentary and 9 more tafsirs.