And the LORD said to Moses, “See, I have made you like God to Pharaoh, and your brother Aaron shall be your prophet. You shall speak all that I command you, and your brother Aaron shall tell Pharaoh to let the people of Israel go out of his land. But I will harden Pharaoh’s heart, and though I multiply my signs and wonders in the land of Egypt, Pharaoh will not listen to you. Then I will lay my hand on Egypt and bring my hosts, my people the children of Israel, out of the land of Egypt by great acts of judgment. The Egyptians shall know that I am the LORD, when I stretch out my hand against Egypt and bring out the people of Israel from among them.” Moses and Aaron did so; they did just as the LORD commanded them. Now Moses was eighty years old, and Aaron eighty-three years old, when they spoke to Pharaoh.
Then the LORD said to Moses and Aaron, “When Pharaoh says to you, ‘Prove yourselves by working a miracle,’ then you shall say to Aaron, ‘Take your staff and cast it down before Pharaoh, that it may become a serpent.’” So Moses and Aaron went to Pharaoh and did just as the LORD commanded. Aaron cast down his staff before Pharaoh and his servants, and it became a serpent. Then Pharaoh summoned the wise men and the sorcerers, and they, the magicians of Egypt, also did the same by their secret arts. For each man cast down his staff, and they became serpents. But Aaron’s staff swallowed up their staffs. Still Pharaoh’s heart was hardened, and he would not listen to them, as the LORD had said. (Exodus 7:1-13 ESV)
Yahweh reiterates for Moses how the process of redeeming Israel is going to work. Moses is to be like God to Pharaoh, commanding him in God’s name (Yahweh) to release His people, speaking through his prophet, Aaron. But God will harden Pharaoh’s heart so that God will have opportunity to multiply the plagues He demonstrates against Egypt. This Yahweh, whom Pharaoh did not know, he will come to know. Moses was 40 years old when he fled Egypt. Now 40 years later he is back to accomplish in God’s power what he could not do in his own.
Moses and Aaron use the first sign God gave them, but Pharaoh’s magicians seem to duplicate it until Moses’ staff turned snake eats theirs up. Because Pharaoh can see his own magicians doing magical things he might tell himself that Moses is simply doing the same. But his magicians and he are hardening their hearts against the truth. God takes responsibility for hardening Pharaoh’s heart but also indicts him for hardening his own heart. As Paul teaches in Romans 9:19, no one resists God’s will and yet God still holds accountable those who do evil. This is fair and just and beyond our ability to understand. Though sovereignty and responsibility seem to contradict, in God’s mind and universe they do not. No one will ever be able to say in the judgment, “God, You made me do the evil I did, so You’re to blame.” We will be held responsible for every decision we make.
In the course of our decision-making we may be called upon by God to trust Him for a miracle. In Moses’ case God told him to do this. God is always the one who determines if a miracle is appropriate or doable. If you are listening to the Lord He will let you know that such a thing is needed and then you must trust Him to do it. This is why it is important to listen in prayer for whether God wants to heal someone or not. I remember during prayer in church one Sunday asking the woman who had come for prayer to listen to what God might be saying to her about her illness. A certain illness had been dismissed as the cause of her problems by a doctor but she thought she heard God saying this was the problem. She returned to the doctor and asked for this to be checked again and that was the problem. God used the doctor to bring the healing. Listen, listen, listen.