The LORD said to Moses, "Get up early in the morning and confront Pharaoh as he goes out to the water. Say to him, This is what the LORD says: Let my people go so that they can worship me.
References for Exodus 8:20
If you refuse to let my people go, I'll send swarms of insects on you, your officials, your people, and your houses. All Egyptian houses will be filled with swarms of insects and also the ground that they cover.
References for Exodus 8:21
But on that day I'll set apart the land of Goshen, where my people live. No swarms of insects will come there so you will know that I, the LORD, am in this land.
I'll put a barrier between my people and your people. This sign will happen tomorrow."
The LORD did this. Great swarms of insects came into the houses of Pharaoh and his officials and into the whole land of Egypt. The land was ruined by the insects.
Then Pharaoh called in Moses and Aaron and said, "Go, offer sacrifices to your God within the land."
Moses replied, "It wouldn't be right to do that, because the sacrifices that we offer to the LORD our God will offend Egyptians. If we openly offer sacrifices that offend Egyptians, won't they stone us to death?
We need to go for a three-day journey into the desert to offer sacrifices to the LORD our God as he has ordered us."
So Pharaoh said, "I'll let you go to offer sacrifices to the LORD your God in the desert, provided you don't go too far away and you pray for me."
Moses said, "I'll leave you now, and I'll pray to the LORD. Tomorrow the swarms of insects will leave Pharaoh, his officials, and his people. Just don't let Pharaoh lie to us again and not let the people go to offer sacrifices to the LORD."
So Moses left Pharaoh and prayed to the LORD.
The LORD did as Moses asked and removed the swarms of insects from Pharaoh, from his officials, and from his people. Not one insect remained.
But Pharaoh was stubborn once again, and he wouldn't let the people go.