وَٱضْمُمْ يَدَكَ إِلَىٰ جَنَاحِكَ تَخْرُجْ بَيْضَآءَ مِنْ غَيْرِ سُوٓءٍ ءَايَةً أُخْرَىٰ
Wadmum yadaka ilaa janaahika takhruj baidaaa'a min ghairi sooo'in Aayatan ukhraa
And draw your hand close to your side — it will come out white, unblemished — another sign,
Wing is the noun used where English would want side, and this command is issued on one further occasion, at 28:32, where the same gesture is prescribed to steady Musa against fear. That same word for wing returns at 15:88 and 26:215, both times in an instruction to lower it over people, meaning deal with them gently. The two signs are shown to the messenger first, before Pharaoh sees either.