What does Exodus 4:6 mean?
God responds to Moses' concern about evidence (Exodus 4:1) by providing miraculous signs. These begin with the ability to throw a staff on the ground, where it will become a snake. When Moses picks it up, the snake turns back into a staff (Exodus 4:2–5). Here, the Lord provides a second sign.The Hebrew term used here is from the root word tsara', which can refer to a wide variety of skin diseases. In modern terms, the condition also called "leprosy" is Hansen's disease. This doesn't generally create white patches. However, fungal infections, rashes, and eczema can create a whitish appearance. The ancient world considered those afflicted with incurable skin disorders as cursed. They were cast out of society for medical and spiritual reasons. After the exodus from Egypt (Exodus 12:41), God will provide medical laws regarding those conditions (Leviticus 13).
In this context, the point of this sign is proving God's control over life and health. The Lord can inflict and restore as He sees fit. Some might dismiss the staff becoming a serpent as a trick. But causing a living body part to instantly vary between horrific disease and health (Exodus 4:7) would be harder to ignore (Exodus 4:8). Unfortunately for Egypt, God's primary demonstration of this divine power over life would be the plague which killed the nation's firstborn (Exodus 12:29–30).