Before the eighth plague of Egypt – the locusts – God commanded Moses to go before Pharaoh: “Go in to Pharaoh, for I have hardened his heart and the heart of his servants, that I may show these signs of mine among them.” (Exodus 10:1)
In the original Hebrew, it is written that God “ichbeed”{הכביד} (translated in
English as hardened) Pharaoh’s heart. This word is derived from the
Hebrew root K-VE-D {כ-ב-ד} which means ‘heavy’.
An interesting interpretation suggests that the use of the concept of
‘heavy’ has a deeper meaning than can first be seen. When Pharaoh witnessed God’s powerful miracles, he was terrified by God and that could have influenced his free will in the decision of letting the people of Israel go or not. In order to keep his free will, God “put heavier weight” on Pharaoh’s heart to balance that and to give him a chance to let the people of Israel go out of his own free will