Exodus 7:16
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 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.
Moses was commissioned to go to Pharaoh as one sent by the LORD God of the Hebrews, the great I AM, to demand the release of Israel. The demand was to let His people go that they might serve and worship Him in the wilderness, with deliverance separating them from bondage and bringing them near to God for His purpose. That service meant separation from the customs, habits, and practices of the world, that they might serve Him and manifest the principles of His kingdom in life and character. The declaration that hitherto he would not hear means Pharaoh had already refused to heed God's command to release the Hebrews to go into the wilderness to serve Him.
The message was delivered at the Nile in connection with the first plague. The Egyptians worshiped the river as a god, and Pharaoh praised it for sustaining lives, crops, and food, so Moses struck the water before Pharaoh and his officials and it became putrid blood for seven days, the fish died, and the people could not use the water. The warning gave Pharaoh advance notice of the coming judgment and the chance to avoid it by obeying and letting the people go. When he refused, God brought the announced judgments, fulfilling the word given to Moses for the king of Egypt with a mighty hand and an outstretched arm, bringing out the Hebrew host from bondage and punishing with total destruction the enemies who refused to listen to His word.
Pharaoh's refusal continued despite the signs and judgments that followed. Neither the rod becoming a serpent nor the river turned to blood moved his hard heart, but only increased his hatred of the Israelites, and the work of the magicians led him to believe these miracles were performed by magic. When the plague of frogs was removed, God left their dead bodies gathered in heaps corrupting the atmosphere rather than causing them to disappear to dust in a moment, lest the king and the Egyptians call the removal magic like the magicians' work. In this Pharaoh and all Egypt had evidence that vain philosophy could not dispose of, that the work was not magic but a judgment from the God of Heaven.
The signs and wonders were produced by the power of God alone, with no human influence or power possessed by Moses in them, and were designed to convince Pharaoh of that divine sending and of his duty to let Israel go that they might serve the living God. The plagues that followed the demand were judgments against Egyptian idolatry that exposed the impotence of Egypt's gods, showed Jehovah's supremacy, and insisted upon Israel's deliverance from bondage. God's purpose was to take His people apart from the world to bring them near to Himself, to prepare them to receive His word and make known to them His will. He led them from Egypt to Mount Sinai, where He revealed His glory and proclaimed with thunder and lightning and terrible majesty the law given in Eden as the transcript of His character, written on tables of stone by the finger of God, so they would manifest the principles of His kingdom in life and character and make known to every nation, kindred, and tongue the principles of His government in heaven and earth.