IN EXODUS 4 two elements introduce complex developments that stretch forward to the rest of the Bible.
The first is the reason God gives as to why Pharaoh will not be impressed by the miracles that Moses performs. God declares, "I will harden his heart so that he will not let the people go" (4:21). During the succeeding chapters, the form of expression varies: not only "I will harden Pharaoh's heart" (7:3), but also "Pharaoh's heart became hard" or "was hard" (7:13, 22; 8:19, etc.) and "he hardened his heart" (8:15, 32, etc). No simple pattern is discernible in these references. On the one hand, we cannot say that the pattern works up from "Pharaoh hardened his heart" to "Pharaoh's heart was hardened" to "God hardened Pharaoh's heart" (as if God's hardening were nothing more than the divine judicial confirmation of a pattern the man had chosen for himself); on the other hand, we cannot say that the pattern simply works down from "God hardened Pharaoh's heart" to "Pharaoh's heart was hardened" to "Pharaoh hardened his heart" (as if Pharaoh's self-imposed hardening was nothing more than the inevitable out-working of the divine decree).
Three observations may shed some light on these texts. (a) Granted the Bible's storyline so far, the assumption is that Pharaoh is already a wicked person. In particular, he has enslaved the covenant people of God. God has not hardened a morally neutral man; he has pronounced judgment on a wicked man. Hell itself is a place where repentance is no longer possible. God's hardening has the effect of imposing that sentence a little earlier than usual. (b) In all human actions, God is never completely passive: this is a theistic universe, such that "God hardens Pharaoh's heart" and "Pharaoh hardened his own heart," far from being disjunctive statements, are mutually complementary. (c) This is not the only passage where this sort of thing is said. See, for instance, 1 Kings 22; Ezekiel 14:9; and above all 2 Thessalonians 2:11-12: "For this reason God sends them a powerful delusion so that they will believe the lie and so that all will be condemned who have not believed the truth but have delighted in wickedness."
The second forward-looking element is the "son" terminology: "Israel is my firstborn son, and I told you, 'Let my son go, so he may worship me.' But you refused to let him go; so I will kill your firstborn son" (Ex. 4:22-23). This first reference to Israel as the son of God develops into a pulsating typology that embraces the Davidic king as the son par excellence, and results in Jesus, the ultimate Son of God, the true Israel and the messianic King.
Exodus 4; Luke 7; Job 21; 1 Corinthians 8