Pharaoh asked this question in reply to Moses' and Aaron's request that he allow Israel to go into the wilderness to hold a feast (Exodus 5:1-2). Pharaoh felt no obligation to obey Jehovah. He was obviously of the common persuasion that every place and people had its own guardian deity.
Israel was a despised and oppressed people. Pharaoh assumed that, among the nations, Israel's God held no higher place than Israel. Pharaoh's ignorance, contempt, and pride were about to bring him face to face with the power of the one true God who would not be mocked by Pharaoh's compromises and broken promises. He was about to learn that Jehovah is the only true and living God, not a powerless, heathen god. Pharaoh's sneering question, "Who is the Lord," would soon be thoroughly and terribly answered. The apostle Paul also answered this question when he declared to the Athenians, "The God that made the world and all things therein, He, being Lord of heaven and earth dwelleth not in temples made with hands..." (Acts 17:24) As "Lord," he exercises authority over His creation. The idea that one God created and rules over everything was completely foreign to Pharaoh's thinking.
God Claims to Be Almighty.
That is, He claims to have the power to do all things. The creation bears evidence to this fact. "In the beginning God created the heaven and the earth." (Genesis 1:1) The Bible began with God. He is "from everlasting to everlasting." (Psalm 90:2) The evolutionist's theory begins with nonliving matter that graduates to life. It is much more reasonable to begin with a living, all-powerful, self-existent God. "Let all the earth fear Jehovah: let all the inhabitants of the world stand in awe of Him. For He spake, and it was done; He commanded, and it stood fast." (Psalm 33:8-9) All of nature's glories, the mysterious wonder of life itself, are enough to show us the might and power of the One who created the "heavens and the earth, the sea, and all that in them is." God's might is just one of the many reasons Pharaoh should have been willing to obey His command to "let my people go."
God Is All-Knowing.
In Job 37:16, we are told that God is perfect in knowledge. God has perfect knowledge of man and all other things. Pharaoh could not outsmart God.
Psalms 139:1-6 says, "O Jehovah, thou hast searched me, and known (me). Thou knowest my down- sitting and mine uprising; Thou understandest my thought afar off. Thou searchest out my path and my lying down, and art acquainted with all my ways. For there is not a word in my tongue, but, lo, O Jehovah, thou knowest it altogether. Thou hast beset me behind and before, and laid thy hand upon me. (Such) knowledge is too wonderful for me; it is high, I cannot attain unto it."
How could Pharaoh play games with God? The Lord even knows the things we think that are not pleasing to Him (cf. Romans 2:16).
He Is All-Wise.
Paul said, "O the depth of the riches both of the wisdom and the knowledge of God! How unsearchable are His judgments, and His ways past tracing out! For who hath known the mind of the Lord? Or who hath been His counselor...For of Him, and through Him, and unto Him, are all things. To him (be) the glory forever. Amen." (Romans 11:33-36)
It was not possible for Pharaoh to match wits with wisdom that so thoroughly exceeds the world's wisdom.
Paul wrote, "The foolishness of God is wiser than men; and the weakness of God is stronger than men." (1 Corinthians 1:25)
Isaiah also declared, "For My thoughts are not your thoughts, neither are your ways My ways, saith Jehovah. For as the heavens are higher than the earth, so are My ways higher than your ways, and My thoughts than your thoughts." (Isaiah 55:8-9)
He Is Omnipresent.
The Psalmist asked, "Whither shall I go from Thy Spirit? Or whither shall I flee from Thy presence? If I ascend up into heaven, Thou art there: if I make my bed in Sheol, behold, Thou art there. If I take the wings of the morning, and dwell in the uttermost parts of the sea; even there shall Thy hand lead me, and Thy right hand shall hold me. If I say, surely the darkness shall overwhelm me, and the light about me shall be night, even the darkness hideth not from Thee, but the night shineth as the day: the darkness and the light are both alike (to Thee)." (Psalm 139:7-12) Pharaoh was about to learn that there was no place he could go to escape his responsibility to God.
He Is a Spirit.
In John 4:24, we read that God is a Spirit, which shows us that He is not bound by the limits of a body of flesh. Pharaoh had to learn the folly of thinking of God as a man. "Thou thoughtest that I was altogether such a One as thyself: (but) I will reprove thee, and set (them) in order before thine eyes." (Psalm 50:21) We cannot understand God by presuming that He is subject to human standards.
He Is True and Just.
The injustices wrought against Israel incurred God's wrath. He is just in every way, so extremely just that, even though He desires for all to be saved, He punishes those who fail to obey His commandments. God is so just that, when man could not reconcile himself back to Him, He sent His Son to die on the cross to do what man could not. God's justice demands that He give the promised reward to the righteous, but it also demands that He give the promised punishment to the unrighteous. The apostle Paul said, "Behold then the goodness and severity of God: toward them that fell, severity ... (Romans 11:22) Pharaoh suffered punishment for his wickedness.
Pharaoh asked, "Who is the Lord, that I should obey His voice?" He certainly was about to find out. God is eternal, He is not limited by time; He is perfect in knowledge; He knows all things; He is almighty, having power to do whatever He wishes; He has supreme wisdom, being able to use all of His qualities in ways that Pharaoh could not comprehend.
He is always present everywhere; there is no way to escape His discerning judgment and wrath. And He is a Spirit, which makes Him free from the bondage of flesh and blood. God is a Being Whose superlative qualities and character attributes caused Pharaoh to see Egypt and all its glory, along with its heathen gods, confounded and rendered helpless by ten plagues (Exodus 7-11) that resulted from his defiance. Indeed, "It is a fearful thing to fall into the hands of the living God." "for our God is a consuming fire." (Hebrews 10:31; 12:29)