1Yahweh said to Moses, “Behold, I have made you as God to Pharaoh; and Aaron your brother shall be your prophet. 2You shall speak all that I command you; and Aaron your brother shall speak to Pharaoh, that he let the children of Israel go out of his land. 3I will harden Pharaoh’s heart, and multiply my signs and my wonders in the land of Egypt. 4But Pharaoh will not listen to you, so I will lay my hand on Egypt, and bring out my armies, my people the children of Israel, out of the land of Egypt by great judgments. 5The Egyptians shall know that I am Yahweh when I stretch out my hand on Egypt, and bring the children of Israel out from among them.”
6Moses and Aaron did so. As Yahweh commanded them, so they did. 7Moses was eighty years old, and Aaron eighty-three years old, when they spoke to Pharaoh.
8Yahweh spoke to Moses and to Aaron, saying, 9“When Pharaoh speaks to you, saying, ‘Perform a miracle!’ then you shall tell Aaron, ‘Take your rod, and cast it down before Pharaoh, and it will become a serpent.’”
10Moses and Aaron went in to Pharaoh, and they did so, as Yahweh had commanded. Aaron cast down his rod before Pharaoh and before his servants, and it became a serpent. 11Then Pharaoh also called for the wise men and the sorcerers. They also, the magicians of Egypt, did the same thing with their enchantments. 12For they each cast down their rods, and they became serpents; but Aaron’s rod swallowed up their rods. 13Pharaoh’s heart was hardened, and he didn’t listen to them, as Yahweh had spoken.
14Yahweh said to Moses, “Pharaoh’s heart is stubborn. He refuses to let the people go. 15Go to Pharaoh in the morning. Behold, he is going out to the water. You shall stand by the river’s bank to meet him. You shall take the rod which was turned to a serpent in your hand. 16You shall tell him, ‘Yahweh, the God of the Hebrews, has sent me to you, saying, “Let my people go, that they may serve me in the wilderness. Behold, until now you haven’t listened.” 17Yahweh says, “In this you shall know that I am Yahweh. Behold: 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. 18The fish that are in the river will die and the river will become foul. The Egyptians will loathe to drink water from the river.”’” 19Yahweh said to Moses, “Tell Aaron, ‘Take your rod, and stretch out your hand over the waters of Egypt, over their rivers, over their streams, and over their pools, and over all their ponds of water, that they may become blood. There will be blood throughout all the land of Egypt, both in vessels of wood and in vessels of stone.’”
20Moses and Aaron did so, as Yahweh commanded; and he lifted up the rod, and struck the waters that were in the river, in the sight of Pharaoh, and in the sight of his servants; and all the waters that were in the river were turned to blood. 21The fish that were in the river died. The river became foul. The Egyptians couldn’t drink water from the river. The blood was throughout all the land of Egypt. 22The magicians of Egypt did the same thing with their enchantments. So Pharaoh’s heart was hardened, and he didn’t listen to them, as Yahweh had spoken. 23Pharaoh turned and went into his house, and he didn’t even take this to heart. 24All the Egyptians dug around the river for water to drink; for they couldn’t drink the river water. 25Seven days were fulfilled, after Yahweh had struck the river.
Aaron was the son of Amram and Jochebed, the brother of Moses and Miriam, and the first priest of Israel. God appointed Aaron to be Moses' spokesman in his audiences with the unnamed Pharaoh of Exodus. As a symbol of his office, Aaron received a magical rod. He turned the rod into a snake - the first in a series of signs, by which he and Moses hoped to persuade Pharaoh to let the Israelites leave Egypt. Aaron also used the rod to call down three of the plagues that followed this first sign (polluting the Nile, frogs and gnats). God also caused the rod to blossom and bear ripe almonds, as a sign that Aaron's descendants would inherit the priesthood.
God summoned Aaron to be present when Moses received the Ten Commandments. But Aaron did not stay on Sinai. Instead he agreed to oversee the casting of an idol (a golden calf) for the Israelites who had rebelled against the authority of the absent Moses.
Aaron was generally a supporter of Moses, but took him to task for his marrying a Cushite wife. For this God rebuked Aaron (and Miriam). His role as priest was critical when he made atonement for the Israelites and stayed the plague that had followed the rebellion of Dathan and Abiram. Exodus and Leviticus give a detailed account of the vestments and duties of Aaron and of his sons.
Aaron's elder sons, Nadab and Abihu, died early but the younger pair, Eleazar and Ithamar, succeeded him in the priesthood. When Aaron was a hundred and twenty three, God instructed him to go up onto Mt. Hor, where he died. Aaron figures prominently in Exodus, Leviticus, Deuteronomy and Numbers, and is named in other books of both Old and New Testaments.