Moses was 80 years old, and Aaron 83 years old, when they spoke to Pharaoh.
The Lord (to Moses): I have made you a god to Pharaoh: and Aaron your brother shall be your prophet. You shall speak all that I command you, and Aaron your brother shall speak to Pharaoh, (and tell him) that he send the children of Israel out of his land. And I will harden Pharaoh’s heart, and multiply my signs and my wonders in the land of Egypt. But Pharaoh shall not listen to you, that I may lay my hand on Egypt, and bring my armies and my people the children of Israel out of the land of Egypt by great judgments. And the Egyptians shall know that I am the Lord, when I stretch out my hand on Egypt, and bring out the children of Israel from among them.
Bible Tools Commentary
I have made you a god – Moses was to act in this business as God’s representative, to act and speak in His name and to perform things beyond the ordinary course of nature.
Aaron your brother shall be your prophet – that is, “interpreter” or “spokesman.” Moses was to be the representative of God, and Aaron was considered the speaker throughout all the upcoming scenes, even though his name is not always expressly mentioned.
Moses and Aaron did as the Lord commanded them.
The Lord (to Moses and to Aaron): When Pharaoh says to you, “Show a miracle,” then you shall say to Aaron, Take your rod, and cast it before Pharaoh, and it shall become a serpent.
Moses and Aaron went in to Pharaoh, and they did as the Lord had commanded. Aaron cast down his rod before Pharaoh and before his servants, and it became a serpent.
Then Pharaoh called the wise men and the sorcerers. The magicians of Egypt also make rods turn into serpents with their enchantments. Every one of them cast down his rod, and they became serpents.
But Aaron’s serpent swallowed up their serpents.
God hardened Pharaoh’s heart, and he did not listen to Moses and Aaron; as the Lord had said.
The Lord (to Moses): Pharaoh’s heart is hardened, he refuses to let the people go. Go to Pharaoh in the morning. He goes out to the water, and you shall stand by the river’s brink where he comes. You shall take in your hand the rod which was turned to a serpent. And you shall say to Pharaoh, The Lord God of the Hebrews has sent me to you, saying, Let my people go, that they may serve me in the wilderness: and, before you would not hear. The Lord says this, In this you shall know that I am the Lord: I will strike with the rod that is in my hand on the waters which are in the river, and they shall be turned to blood. And the fish that is in the river shall die, and the river shall stink; and the Egyptians shall loathe to drink of the water of the river.
Note: I’ve heard that Pharaoh went to the river every morning to worship the river god.
The Lord (to Moses): Say to Aaron, Take your rod, and stretch out your hand on the waters of Egypt, on their streams, on their rivers, and on their ponds, and on all their pools of water, that they may become blood; and that there may be blood throughout all the land of Egypt, even in their vessels of wood and stone.
Moses and Aaron did as the Lord commanded. Aaron lifted up the rod and struck the water in the river, in the sight of Pharaoh and his servants; and all the waters that were in the river were turned to blood. And the fish that were in the river died; and the river stank, and the Egyptians could not drink the water of the river; and there was blood throughout all the land of Egypt.
And the magicians of Egypt changed water to blood with their enchantments. And Pharaoh’s heart was hardened, and he did not listen to Moses and Aaron; as the Lord had said.
Pharaoh turned and went into his house, and he did not take this to heart.
Note: God knew beforehand that the magicians of Egypt could duplicate these signs. He knew that Pharaoh would not believe in His power after the magicians repeated the signs.
And all the Egyptians dug around the river for water to drink; because they could not drink of the water of the river.
And seven days were fulfilled, after that the Lord had struck the river.