Tafsir of Ash-Shu`ara' 26:33

"And he drew out his hand" from his garment (bosom).

"And behold, it was white for the observers"—that is, its whiteness was such that observers would gather to gaze at it because it departed from the ordinary. It was a radiant, luminous whiteness. It is narrated that when he witnessed the matter of the staff, he said, "Is there anything else?" So he (peace be upon him) brought out his hand, and [Pharaoh] asked, "What is this?" He replied, "My hand." He then inserted it into his armpit and drew it out, and it had a radiance that almost blinded the sight and filled the horizon.