20 Now the LORD said to Moses, "Rise early in the morning and present yourself before Pharaoh, as he comes out to the water, and say to him, 'Thus says the LORD, "Let My people go, that they may serve Me. 21 "For if you do not let My people go, behold, I will send swarms of flies on you and on your servants and on your people and into your houses; and the houses of the Egyptians will be full of swarms of flies, and also the ground on which they dwell. 22 "But on that day I will set apart the land of Goshen, where My people are living, so that no swarms of flies will be there, in order that you may know that I, the LORD, am in the midst of the land. 23 "I will put a division between My people and your people. Tomorrow this sign will occur."'" 24 Then the LORD did so. And there came great swarms of flies into the house of Pharaoh and the houses of his servants and the land was laid waste because of the swarms of flies in all the land of Egypt.
25 Pharaoh called for Moses and Aaron and said, "Go, sacrifice to your God within the land." 26 But Moses said, "It is not right to do so, for we will sacrifice to the LORD our God what is an abomination to the Egyptians. If we sacrifice what is an abomination to the Egyptians before their eyes, will they not then stone us? 27 "We must go a three days' journey into the wilderness and sacrifice to the LORD our God as He commands us." 28 Pharaoh said, "I will let you go, that you may sacrifice to the LORD your God in the wilderness; only you shall not go very far away Make supplication for me." 29 Then Moses said, "Behold, I am going out from you, and I shall make supplication to the LORD that the swarms of flies may depart from Pharaoh, from his servants, and from his people tomorrow; only do not let Pharaoh deal deceitfully again in not letting the people go to sacrifice to the LORD." 30 So Moses went out from Pharaoh and made supplication to the LORD. 31 The LORD did as Moses asked, and removed the swarms of flies from Pharaoh, from his servants and from his people; not one remained. 32 But Pharaoh hardened his heart this time also, and he did not let the people go.