Exodus 8:1

"And they shall hearken to thy voice: and thou shalt come, thou and the elders of Israel, unto the king of Egypt, and ye shall say unto him, The LORD God of the Hebrews hath met with us: and now let us go, we beseech thee, three days' journey into the wilderness, that we may sacrifice to the LORD our God."

"And he said, Certainly I will be with thee; and this shall be a token unto thee, that I have sent thee: When thou hast brought forth the people out of Egypt, ye shall serve God upon this mountain."

"And afterward Moses and Aaron went in, and told Pharaoh, Thus saith the LORD God of Israel, Let my people go, that they may hold a feast unto me in the wilderness."

"And thou shalt say unto him, The LORD God of the Hebrews hath sent me unto thee, saying, Let my people go, that they may serve me in the wilderness: and, behold, hitherto thou wouldest not hear."

"And I say unto thee, Let my son go, that he may serve me: and if thou refuse to let him go, behold, I will slay thy son, even thy firstborn."