What does Exodus 4:21 mean?

This summarizes the struggle to free Israel from Egyptian slavery (Exodus 1:13–14, 22). Moses (Exodus 3:10) is sent to perform miraculous signs meant to convince Pharaoh to release the Hebrews. These acts (Exodus 4:2–9) summarize the Lord's power over animal life, human life, and nature itself. The interactions with Pharaoh will also explore the relationship between human will and God's all-knowing, all-powerful control. Pharaoh will be given a choice, but God also plans to bring judgment on Egypt.

God warns that Pharaoh will not cooperate with Moses. In fact, the Lord plans to make Pharaoh stubborn, in order to set up further proof of divine power (Exodus 4:22–23; 12:29–30). This may seem unfair. However, Proverbs 29:1 warns about what happens when someone habitually defies God. Eventually, they reach a point where God's mercy is no longer offered, and instead they are subjected to consequences and judgment. Scripture makes it clear that Pharaoh chooses stubbornness first (Exodus 5:2; 7:14, 22). In fact, he repeatedly hardens his own heart against the Lord (Exodus 8:15, 19, 32; 9:7). Only after many such instances does God begin to make an example of the Egyptian ruler (Exodus 9:12; 10:1, 20, 27; 11:10), as predicted here.