Verses 8-13 ” 8And the LORD spake unto Moses and unto Aaron, saying,
9When Pharaoh shall speak unto you, saying, Shew a miracle for you: then thou shalt say unto Aaron, Take thy rod, and cast it before Pharaoh, and it shall become a serpent.
10And Moses and Aaron went in unto Pharaoh, and they did so as the LORD had commanded: and Aaron cast down his rod before Pharaoh, and before his servants, and it became a serpent.
11Then Pharaoh also called the wise men and the sorcerers: now the magicians of Egypt, they also did in like manner with their enchantments.
12For they cast down every man his rod, and they became serpents: but Aaron’s rod swallowed up their rods.
13And he hardened Pharaoh’s heart, that he hearkened not unto them; as the LORD had said.”
When Pharaoh saw the miracle performed with Aaron’s rod his heart became bitter and more hard against God. This is the result of pride; and it reminds us that we should admit it when we are wrong and God is right– something our fleshly nature does not want to do.