Exodus 8:28-29

28Pharaoh responded, “I will let you go and sacrifice to the Lord your God in the wilderness, but don’t go very far. Make an appeal for me.”

29“As soon as I leave you,” Moses said, “I will appeal to the Lord, and tomorrow the swarms of flies will depart from Pharaoh, his officials, and his people. But Pharaoh must not act deceptively again by refusing to let the people go and sacrifice to the Lord.”