Exodus 4:21 (KJV) states, "And the Lord said unto Moses, When thou goest to return into Egypt, see that thou do all those wonders before Pharaoh, which I have put in thine hand: but I will harden his heart, that he shall not let the people go."

This verse is a pivotal moment in the story of the Exodus, as it marks the beginning of the interaction between Moses and Pharaoh, and is a significant shift in the trajectory of the Israelites' journey from slavery to freedom. In this verse, God is speaking directly to Moses, instructing him on how to approach Pharaoh and what wonders to perform in order to convince him to let the Israelites go. However, God also informs Moses that He will harden Pharaoh's heart, ensuring that he will not easily relent and allow the Israelites to leave.

One of the important themes present in this verse is the idea of God's sovereignty and control over the hearts of individuals. The hardening of Pharaoh's heart is a complex theological concept that has sparked much debate and interpretation over the centuries. Some people interpret this as a way of emphasizing God's power and authority over the rulers of the earth, while others see it as a demonstration of God's justice and the consequences that come from choosing to defy Him.

The context of this verse is the beginning of a series of confrontations between Moses and Pharaoh that ultimately lead to the ten plagues and, eventually, the release of the Israelites from slavery. The hardening of Pharaoh's heart plays a crucial role in this narrative, as it sets the stage for the subsequent events that unfold. It serves as a reminder of the tension and struggle between the will of God and the will of man, and the ultimate triumph of God's plan despite the obstacles presented by human resistance.

In terms of symbolism, this verse represents the ongoing struggle between good and evil, and the stubbornness and resistance that often accompanies human pride and arrogance. Pharaoh's hardened heart symbolizes the obstinance and reluctance to change that often accompanies a position of power and authority. On a deeper level, it also serves as a reminder of the spiritual hardening of the heart that can occur when one repeatedly chooses to turn away from God and His commandments.

In a broader theological context, this verse also raises questions about the nature of free will and predestination. Some people interpret the hardening of Pharaoh's heart as a demonstration of God's foreknowledge and preordained plan, while others see it as a reflection of Pharaoh's own choices and the consequences that naturally follow.

In sum, Exodus 4:21 (KJV) is a verse that encapsulates the tension and drama of the confrontation between Moses and Pharaoh, and the complex theological themes of God's sovereignty, human resistance, and the ongoing struggle between good and evil. It serves as a reminder of the power and authority of God, as well as the stubbornness and pride that can hinder the hearts of humanity. It also invites deeper reflection on the nature of free will and predestination, and the consequences that come from choosing to follow or defy the will of God.