Exodus 4:6

His hand was leprous as snow. — The worst form of leprosy was called by the Greeks λεύκη, “the white disease.” When it is fully developed, the whole skin appears glossy white, and every hair is “white like wool” (Celsus, De Re Medica, v. 28, § 12). This form is said to be absolutely incurable. It was probably from the fact of Moses exhibiting a leprous hand that the Egyptians called the Israelites “the lepers,” as related by Manetho (ap. Joseph. contra Ap. i. 26), Chæremon (ibid., i. 32), and others.