Exodus 7:10-13

So Moses and Aaron came to Pharaoh, and thus they did just as the LORD had commanded; and Aaron threw his staff down before Pharaoh and his servants, and it became a serpent. Then Pharaoh also called for the wise men and the sorcerers, and they also, the magicians of Egypt, did the same with their secret arts. For each one threw down his staff and they turned into serpents. But Aaron's staff swallowed up their staffs. Yet Pharaoh's heart was hardened, and he did not listen to them, as the LORD had said.

God had told Moses to go and perform signs and miracles before Pharaoh so that he might let the people go and worship Him in the wilderness. One of these miracles was to turn his staff into a snake. While miraculous, it seems that Pharaoh's magicians could duplicate the effect, taking away the impact of the miracle on Pharaoh. However, note that they did not remove the one snake, but made more snakes. If you think about it, it doesn't really help the situation very much. The one snake could have bitten someone and killed them, but more snakes just added to the problem! Isn't it interesting that often times, man can duplicate many of the things that God can do, but most of the time, it just adds to the noise and confusion rather than makes it clearer? It's only when God's work produces fruit of righteousness that we can truly see clearly what is from God and what isn't. While God's work created the initial problem for Pharaoh and the magicians only added to it, it was God's work that cleared up the problem and protected Pharaoh in the end. Likewise, it is God's work alone that will eventually clear up the confusion and reveal the truth of God's greatness. The work of man will simply confuse and muddy the waters of our search for truth. Don't be fooled by things that appear to be from God. Test it, and only if it proves true, then believe it.