Tafsir of Al-A'raf 7:108

"And he drew out his hand..." (meaning he brought it out from his bosom, based on His saying, the Exalted: "Insert your hand into your bosom," or from under his armpit, based on His saying, the Glorified: "And draw your hand close to your side." Reconciling the two is possible within the same timeframe, and it was the right hand, as explicitly stated in some traditions.)

"...and lo, it was white to the beholders" (meaning white with a luminous whiteness that transcends the norm, which onlookers would gather to see. It has been narrated that it illuminated for him what was between the heaven and the earth. It has also come in a report that he showed Pharaoh his hand and said [peace be upon him]: "What is this?" He replied: "Your hand." Then he inserted it into his bosom—wearing a wool cloak—and drew it out, and lo, it was white with a luminous whiteness whose radiance overcame the radiance of the sun.)

It has been said: The meaning is "white for the sake of the beholders," not that it was white in its original creation, for he [peace be upon him] was brown-skinned, of deep complexion. Al-Bukhari extracted from Ibn Umar who said: The Messenger of Allah [may Allah bless him and grant him peace] said: "As for Musa, he was brown-skinned, large-bodied, with straight hair, as if he were from the men of the Zutt." By "Zutt," he [peace be upon him] meant a race of people from the Sudan and the Indians. Some have specified that this whiteness was only in the palm, and the application of the word "hand" to it is literal.

In al-Qamus: The hand is the palm, or from the tips of the fingers to the palm. Its root is yaday, as evidenced by its plural aydi. The [form] yad does not occur when appended to a pronoun, due to what has been established in its proper place. It has appeared in their speech as yadd with tashdid, which is a dialectal variation thereof.