Then the LORD spoke to Moses. He said, "Get up early in the morning. Talk to Pharaoh as he goes down to the river. Say to him, 'The LORD says, "Let my people go. Then they will be able to worship me.
References for Exodus 8:20
If you do not let my people go, I will send large numbers of flies. I will send them on you and your officials. I will send them on your people and into your homes. The houses of the Egyptians will be full of flies. Even the area where they live will be full of flies.
" ' "But on that day I will treat the area of Goshen differently from yours. That is where my people live. There will not be large numbers of flies in Goshen. Then you will know that I, the Lord, am in this land.
I will treat my people differently from yours. The miraculous sign will take place tomorrow." ' "
So the LORD did it. Huge numbers of flies poured into Pharaoh's palace. They came into the homes of his officials. All over Egypt the flies destroyed the land.
Then Pharaoh sent for Moses and Aaron. He said to them, "Go. Offer sacrifices to your God here in the land."
But Moses said, "That wouldn't be right. The sacrifices we offer to the LORD our God wouldn't be accepted by the Egyptians because of their beliefs. Suppose we offered sacrifices they couldn't accept. Then they would throw stones at us and try to kill us.
We have to take a journey that lasts about three days. We want to go into the desert to offer sacrifices to the LORD our God, exactly as he commands us."
Pharaoh said, "I will let you and your people go to offer sacrifices. You can offer them to the LORD your God in the desert. But you must not go very far. And pray for me."
Moses replied, "As soon as I leave you, I will pray to the Lord. Tomorrow the flies will leave you. They will also leave your officials and your people. Just be sure you don't try to trick us again. Let the people go to offer sacrifices to the Lord."
Then Moses left Pharaoh and prayed to the Lord.
And the LORD did what Moses asked. The flies left Pharaoh, his officials and his people. Not one fly remained.
But Pharaoh's heart became stubborn that time also. He wouldn't let the people go.