Exodus 8:27

We will go three days’ journey into the wilderness, and sacrifice to the LORD our God, as he shall command us.

Moses refused to sacrifice inside Egypt and insisted that Israel must go three days' journey into the wilderness to sacrifice to the Lord as God commanded. Sacrificing in Egypt would be improper because Israel would offer before the Egyptians' eyes what was detestable to them, animals the Egyptians worshiped as sacred. The Egyptians treated killing such an animal, even by accident, as an unforgivable offense answerable only by the offender's life, so Israelites sacrificing in their sight would face death by stoning and be in danger from their masters.

Pharaoh consented to the wilderness journey only while under the chastening of the plague of flies, asking Moses and Aaron to pray for its removal. He permitted the sacrifice in the wilderness only on condition that Israel would not go very far away. Moses agreed to ask the Lord to remove the flies the next day, while warning Pharaoh not to act deceptively by again refusing to let the people go to sacrifice. When the plague ceased, Pharaoh broke his agreement and again refused to let Israel go.

Pharaoh's response illustrates a pattern of resistance under plague pressure, offering only partial concessions — first sacrifice in Egypt, then the men alone, then women and children without livestock — rather than full obedience to God's command. In its larger setting, the demand belongs to the plague account in which the plagues exposed the helplessness of Egypt's idols and Israel's release was required so the people could serve and worship God.