Ephesians 4:18 Having the understanding darkened, being alienated from the life of God through the ignorance that is in them, because of the blindness of their heart:
The word “blindness” is translated as “hardness” in other places.
Mark 3:5 And when he had looked round about on them with anger, being grieved for the hardness of their hearts, he saith unto the man, Stretch forth thine hand. And he stretched it out: and his hand was restored whole as the other.
Romans 11:25 For I would not, brethren, that ye should be ignorant of this mystery, lest ye should be wise in your own conceits; that blindness in part is happened to Israel, until the fulness of the Gentiles be come in.
Prime example we have of someone’s heart hardening is Pharaoh (Ex. 4:21;7:3,13-14,22;8:15,19,32;9:7,12,34-35,10:1,20,27;11:10;14:4,8,17)
Exodus 4:21 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.
Pharaoh would not let the people of Israel go. God hardened his heart after every miracle that took place. Likewise, when we try to share the gospel with unbelievers most people will not receive the truth of the gospel. Instead, they reject it and therefore their hearts harden each time they are exposed to it and reject it. But then there are the few that will believe it.
While unbelievers’ hearts harden towards God and the gospel, their hearts soften towards the world and sin. While believers, on the other hand, soften their hearts towards God and the gospel, and harden their hearts towards sin (or at least they should). I’m talking here about believers not partaking of sinful behaviors like the rest of the world does. I’m not talking about hardening our hearts towards them in the sense that we don’t minister to them. We should of course minister to them. Some men’s hearts become like butter when exposed to heat (God’s Word, the truth, the gospel) and they start to melt or soften towards it. Others are like clay where they harden every time they are exposed to the truth.
Our job as ambassadors of Christ, is to keep preaching/teaching/sharing the gospel with the world. Paul tells the Corinthians that he didn’t come with excellence of speech or of wisdom. But, instead he determined not to know anything except Jesus Christ and Him crucified (1 Cor. 2:1-2).
The preaching of the cross will be foolishness to the world. They will think of you as a fool. But, you and I know that it is the power of God and the wisdom of God (1 Cor. 1:18-25). For it is the power of God unto salvation to every one that believes it (Rom. 1:16). So, don’t give up! Keep sharing the gospel! The more times we expose unbelievers to the truth, the more times they will hear it, and the more times they hear it, the greater the chance that they might open their heart to God’s Word and believe the gospel. Our job is to share. Let the Holy Spirit do His job by opening up their heart and saving them.
Romans 10:15 And how shall they preach, except they be sent? as it is written, How beautiful are the feet of them that preach the gospel of peace, and bring glad tidings of good things!
Ephesians 6:10-20 Finally, my brethren, be strong in the Lord, and in the power of his might. Put on the whole armour of God, that ye may be able to stand against the wiles of the devil. For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places. Wherefore take unto you the whole armour of God, that ye may be able to withstand in the evil day, and having done all, to stand. Stand therefore, having your loins girt about with truth, and having on the breastplate of righteousness; And your feet shod with the preparation of the gospel of peace; Above all, taking the shield of faith, wherewith ye shall be able to quench all the fiery darts of the wicked. And take the helmet of salvation, and the sword of the Spirit, which is the word of God: Praying always with all prayer and supplication in the Spirit, and watching thereunto with all perseverance and supplication for all saints; And for me, that utterance may be given unto me, that I may open my mouth boldly, to make known the mystery of the gospel, For which I am an ambassador in bonds: that therein I may speak boldly, as I ought to speak.