In Parshat Shmot we read about when God appears to Moshe at the burning bush. Moshe asks God how the Jewish people will believe that he was sent by God. God tells him (Shmot 4:3) “Throw it (the rod) on the ground. He threw it on the ground and it turned into a nachash (snake)…”

In our Parsha, Vaera (Shmot 7:9) God told Moshe and Aharon: “When Pharaoh speaks to you, saying, ‘Give yourselves [credibility by displaying] a marvel; you should then say to Aharon, ‘Take your rod and throw it down before Pharaoh. It will become a tanin (dragon or crocodile).”

Why was Pharoah given the sign of the tanin while Moshe was given the sign of the nachash?

According to Cassuto: Instead of the nachash (snake), most appropriate to desert, in which form the sign was transmitted to Moshe, comes here the tanin (dragon or crocodile), most appropriate to the Egyptian milieu.

The Midrash, Torah Shlema by Rav Kasher explains that there is a deeper meaning:

God said: This villain boasts and calls himself a tanin as it says in Yechezkel 29:3 “Thus says God; behold, I am against you, Pharaoh, King of Egypt, the great tanim that couches in the midst of his rivers (the Nile and its canals) who has said, My Nile river is my own, and I have made it for myself.” Go tell him: See this staff, it is a piece of dry wood; it will become a tanin with life and soul and swallow up the other staffs and it is destined to revert to a dry piece of wood. You, Pharaoh, likewise, I created from a putrid drop and gave you empire and you boasted and said “My Nile river is my own, and I have made it for myself.” Behold I shall turn you back to nothingness and chaos.

Unfortunately, Pharaoh looked at himself as a God and didn’t learn from the message that was hinted to. Pharaoh remained haughty and his downfall eventually did come.

The lesson that can be learned here is that no matter how much we may have accomplished we must not be haughty because at the end of the day, everything that we have comes from God and everything is in God’s hands.