The intent of the second sign.
If the first sign was powerful to convince, the second was still more powerful (Exodus 4:8). It showed Moses able to produce, and cure, in a moment of time, the most virulent malady to which human nature was liable. The Egyptians greatly feared leprosy, and declared in their own accounts of the Exodus that they drove the Israelites out of their country because they were afflicted with that loathsome disease. The Israelites regarded it as the worst affliction that could befall a man. The hand of Moses made leprous within the folds of the garment that enwrapped his bosom typified perhaps the Israelitish nation, corrupted by the circumstances that enwrapped it around in Egypt. The cure indicated that Moses would, through the power committed to him, cleanse the people from their defilements, and. restore them to a state of spiritual soundness. Thus it was at once a warning and a promise. The sign appears not to have been used in Moses' dealings with the Egyptians (Exodus 7:10-17), because it was inappropriate as respected them, since they were beyond cleansing—there was no healing of their wound. Thus by this sign were taught two things:
1. That there is a fountain opened for sin and for uncleanness which can wash away, under the condition of repentance, any defilement; and
2. That there is a state of sinfulness and corruption when repentance ceases to be possible, and the moral nature can no longer be restored, and nothing remains but that fearful looking-for of judgment to come whereof the Epistle to the Hebrews speaks (Exodus 10:27). The signs of the serpent and the blood—signs of judgment—were for the Egyptians and the Israelites alike; the sign of the hand made leprous and then restored—a sign of mercy—was for the Israelites only.