The Hand of Musa turning White without any Disease
This is the second sign of Musa. That is Allah has commanded him to place his hand into the opening of his garment, as is clearly stated in another Ayah. It mentioned here merely as a passing reference, saying:
وَاضْمُمْ يَدَكَ إِلَى جَنَاحِكَ
(And press your hand to your side:) Allah said in another Ayah,
(And draw your hand close to your side to be free from fear. These are two signs from your Lord to Fir`awn and his chiefs.) 28:32 Mujahid said,
وَاضْمُمْ يَدَكَ إِلَى جَنَاحِكَ
(And press your hand to your side:) "This means put your palm under your upper arm." When Musa put his hand into the opening of his garment and brought it out, it came out shining as if it were a half moon. Concerning His statement,
The third prayer وَاحْلُلْ عُقْدَةً مِّن لِّسَانِي يَفْقَهُوا قَوْلِي (And remove the knot from my tongue, that they may understand my speech - 20:27, 28). The story behind this "knot" is that as an infant Sayyidna Musa (علیہ السلام) lived with his own mother who used to suckle him and was paid for her services by the Pharaoh. When he was weaned, the Pharaoh and his wife 'Asiya ؓ adopted him, and took him away from his mother. One day Sayyidna Musa (علیہ السلام) caught hold of the Pharaoh's beard and slapped him on the face. Another version has it that he was playing with a stick and with it he struck the Pharaoh on his head. The Pharaoh was enraged and made up his mind to put him to death. His wife 'Asiya ؓ tried to pacify him and said, "0 King! Why do you take this matter so seriously? After all he is merely a child who does not understand things. You can test him if you like and you will find that he cannot distinguish between good things and bad things".
Incidents in the lives of prophets of the past are mentioned in the Bible as well as in the Quran. But, at many places, there are meaningful differences in the versions respectively of the Quran and the Bible. For instance, in this case, the Bible says: Moses kept his hand on his chest and covered it, and when he brought it out and saw it, it was white like ice, due to leprosy (Exodus 4:7). The Bible attributes the whiteness of Moses’s hand to ‘leprosy’. In this context, the Quran’s describing of the miracle of the white hand and the adding of the words ‘without any blemish’ clearly indicate that the Qur’an is not derived from the Bible, but is directly from God, who is All-knowing. As such, it corrects the biblical version. Moses was given two special miracles. The miracle of the snake was the sign of power, and the miracle of the bright white hand was a symbol of his standing for a luminous Truth. Pharaoh transgressed all limits when, having attained power, he considered himself to be god. The literal meaning of ‘Pharaoh’ is the child of the sun. The ancient Egyptians used to regard the sun as the greatest god–the Mighty Lord. So Pharaoh had declared himself the representative of the sun god on earth. He had statues of himself made and installed in all the cities of Egypt and these statues were worshipped. Power is a blessing conferred by God; when a man receives this blessing, he should be overwhelmed with gratitude. But if he is vain and arrogant, he not only feels no gratitude, but he also sets himself up as God’s equal.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.