What does Exodus 4:7 mean?
The Lord has given Moses a sign which proves that his mission is legitimate (Exodus 4:1). This involved turning his staff into a snake and back (Exodus 4:2–5). The second demonstration begins with Moses placing a healthy hand under the fold of his robe near his chest; when he removes it, it is horrifically riddled with disease (Exodus 4:6). Most English translations use the term "leprosy," though the Hebrew term itself includes a wide variety of conditions. Moses follows God's directions to cover and uncover his hand again, and it is entirely cured.Changing a staff into a snake, and then reversing it, might have been dismissed as a trick or duplicated with some unknown means (Exodus 7:11–12). Instantly afflicting a healthy hand, then healing it, would be much harder to dismiss (Exodus 4:8).
The third sign given to Moses involves turning water into blood (Exodus 4:9). Combined, these miracles indicate the Lord's absolute power over animal life, human life, and all of nature. This foreshadows the pattern of plagues (Exodus 3:20) which prove the Lord's superiority over the powers of supposed Egyptian deities.