Then the Lord spoke to Moses: Early tomorrow morning present yourself to Pharaoh when he sets out toward the water, and say to him: Thus says the Lord: Let my people go to serve me.

For if you do not let my people go, I will send swarms of flies upon you and your servants and your people and your houses. The houses of the Egyptians and the very ground on which they stand will be filled with swarms of flies.

But on that day I will make an exception of the land of Goshen, where my people are, and no swarms of flies will be there, so that you may know that I the Lord am in the midst of the land.

I will make a distinction between my people and your people. This sign will take place tomorrow.

This the Lord did. Thick swarms of flies entered the house of Pharaoh and the houses of his servants; throughout Egypt the land was devastated on account of the swarms of flies.

Then Pharaoh summoned Moses and Aaron and said, “Go sacrifice to your God within the land.”

But Moses replied, “It is not right to do so, for what we sacrifice to the Lord, our God, is abhorrent to the Egyptians. If we sacrifice what is abhorrent to the Egyptians before their very eyes, will they not stone us?

We must go a three days’ journey in the wilderness and sacrifice to the Lord, our God, as he commands us.”

Pharaoh said, “I will let you go to sacrifice to the Lord, your God, in the wilderness, provided that you do not go too far away. Pray for me.”

Moses answered, “As soon as I leave you I will pray to the Lord that the swarms of flies may depart tomorrow from Pharaoh, his servants, and his people. Pharaoh, however, must not act deceitfully again and refuse to let the people go to sacrifice to the Lord.”

When Moses left Pharaoh, he prayed to the Lord; and the Lord did as Moses had asked, removing the swarms of flies from Pharaoh, his servants, and his people. Not one remained.

But once more Pharaoh became obstinate and would not let the people go.