Exodus 14:8 And the Lord hardened the heart of Pharaoh king of Egypt, and he pursued after the children of Israel: and the children out with an high hand.
Pharaoh proved that His previous repenting and relenting was shallow and insincere, changing his mind again to pursue after Israel. After resisting God in unbelief and hardening his heart many times, God hardened Pharaoh’s heart. And when that happens it’s too late. And now with a firmly solid heart against God’s judgment and mercy, he regretted relenting and tried to get his slave labor back again.
We Christians may wonder at and even mock unbelievers who resist the Holy Spirit, ignore Jesus, spurn the love of God, and reject the Gospel. However, we should look at our own hearts and admit to the hardness that is still there. Even godly believers retain a residue of hardness that pridefully resists the judgments of the Law and can’t fully believe the unconditional forgiveness, amazing compassion, and absolute love of God.
It easier to change our mind and fall back to the old ways than we would like to admit or confess. The temptations of the devil, the world, and our sinful flesh are more powerful and ever present than we would like to believe. For this reason repentance and faith, or conversion, is not just a once and done deal. Thus we are constantly on guard lest the heart becomes harder. Daily repentance is the best preventative. We respond by confessing a Pharaohic heart and receiving eternal forgiveness and grace to help.