What does Exodus 5:2 mean?

The very first request about freedom for Israel (Exodus 3:18; 5:1) was explicitly given as a command from "the Lord, the God of Israel." This is not merely a favor; it is an order from a particular deity. Though the eventual goal is Israel's liberation (Exodus 3:20), the first request is for time to go into the wilderness to worship. The only consequences threatened are against the Hebrews themselves (Exodus 5:3). But as expected (Exodus 3:19), Pharaoh refuses. He goes even further, showing disrespect to God. His question, "who is the Lord?" is not an appeal for more information. It's a rhetorical way of saying, "this 'Lord' is nothing to me."

Pharaoh has no belief in the God of Israel, nor any desire to obey Him. In many ways, his response makes sense. He worships Egyptian gods and knows nothing about the deity of Abraham, Isaac, and Jacob. He has no incentive to release slave labor. Further, he has enough common sense to know that if the entire Hebrew population leaves, there is no guarantee they will come back.

Yet this is not simple skepticism; Pharaoh will repeatedly refuse to release the people despite miracles and catastrophes (Exodus 8:15, 19, 32; 9:7). Eventually, God will begin amplifying the king's stubbornness as a form of judgment (Exodus 4:21; 9:12; 10:1, 20, 27; 11:10). Pharaoh's immediate response reveals a petty, vindictive nature (Exodus 5:6–9).