Exodus 8:28
And Pharaoh said, I will let you go, that ye may sacrifice to the LORD your God in the wilderness; only ye shall not go very far away: intreat for me. And Pharaoh said, I will let you go, that ye may sacrifice to the LORD your God in the wilderness; only ye shall not go very far away: intreat for me.
This was Pharaoh's second compromise, offered after his first proposal that Israel sacrifice inside Egypt was refused. The journey into the wilderness was necessary because the animals Israel had to sacrifice were sacred to the Egyptians, and to kill one even accidentally was punishable by death, so sacrificing before Egyptian eyes in Egypt would give offense as an abomination and bring stoning. While under the plague of swarms of flies, Pharaoh yielded enough to consent to Israel going three days' journey into the wilderness to sacrifice to the Lord their God as commanded, but he added the condition that they must not go very far away, and he asked for intercession for himself. Moses agreed to go out and entreat the Lord that the swarms of flies would depart on the next day from Pharaoh, his servants and his people, while warning Pharaoh not to deal deceitfully any more by refusing to let the people go to sacrifice.
God acted according to the word of Moses and removed the plague completely, so that not one fly remained. Pharaoh's promise was not trustworthy, for he yielded only while under God's chastening hand, and after the plague ended he hardened his heart through persistent rebellion and again refused to let the people go as God required. He made only limited concessions under affliction, and those concessions grew only as the plagues grew more severe. His offer to let Israel worship while trying to restrict their departure came amid judgments that exposed the powerlessness of Egypt's idols, showed the supremacy of the Lord, and insisted on Israel's deliverance.