ויהי לנחש. מפני מה הראה לו ית' נחש יותר מדבר אחר אלא מה נחש נושך וממית כך פרעה ועבדיו נושכין וממיתין את ישראל ומה ששב מטה רמז שיהא פרעה ועבדיו יבשין כעץ, וידו שהיתה מצורעת שכך פרעה ועבדיו טמאין ומטמאין את ישראל והנה שבה כבשרו רמז שיטהרו ישראל מטומאת מצרים: ויהי לנחש, “it turned into a serpent.” Why did G–d show Moses this miracle by using a serpent rather than any other creature? It symbolised that just as the bite of a snake not only hurts but results in the death of the victim, so Pharaoh and his servants would not only “bite” the Hebrews but would by their treatment of them cause their deaths. Moses being asked to grasp the tail of that serpent and turn it back into his staff, was to symbolise that Pharaoh and his servants would become dried out as the wood of his staff. Any hand afflicted with the plague of tzoraat had automatically become ritually unclean, as we know from Leviticus 14,6. Moses placing his hand back within the folds of his tunic symbolically restores the entire Jewish people to ritual purity which it had lost through contact with the Egyptians. When the Torah reports in verse 7 that והנה שבה כבשרו, “and lo, his hand looked again like the rest of his flesh,“ this was a hint that the Jewish people’s state of ritual impurity would be reversed.