Q. Is it possible for a person whose heart has become hardened, and been hardened even further by God, to come back to God?
I’m not exactly sure what you mean by God hardening someone’s heart even further. We do have a record in the Bible of God hardening Pharaoh’s heart. But that was for a specific purpose. Pharaoh had already set himself up against God, as became clear from his first answer to Moses: “Who is the Lord, that I should obey him and let Israel go? I do not know the Lord and I will not let Israel go.” So this was a matter of God confirming Pharaoh in choices that he had already made, but that was for the purpose of God showing who he was to all the world through what he did to what was then the greatest empire in the world. We know that this made an impression on all the surrounding peoples, because later one of them told the Israelites how they had heard of what God had done to the Egyptians, and as a result, they knew that “the Lord your God is God in heaven above and on the earth below.”
But I would say that, apart from such extraordinary purposes within God’s historical plan of redemption, God would not harden the heart of an individual so as to make it harder for that individual to repent and return. Sometimes God will confirm us in our choices in the sense of allowing us to experience the consequences of those choices. But God does that specifically so that we will realize that they were the wrong choices and repent.
So my essential answer to your question is yes, a person whose heart has become hardened can indeed return to God. Specifically if you are asking about yourself, the very fact that you are asking shows that your heart has begun to soften. You want to know if there is a way back to God. And there always is, for anyone who desires to return. The door is always open on God’s side. As the Bible says, “God was in Christ, reconciling the world to himself, no longer counting people’s sins against them.” God is eager to forgive and to restore us to relationship to him. So if you are asking about yourself, I would encourage you that the way is genuinely open for you to return to God.
And even if you are asking about someone else, the fact that God has put this person on your heart and you are wondering if there is still hope suggests to me that God, through his Holy Spirit, is reaching out to the person through you, wanting you to pray and intercede for that person. So I would encourage you to do that. See your concern for the person as something that God has given you because God is concerned and knows that you will pray and perhaps be someone who is able to encourage and help the person to return.
Only God truly knows what is in a person’s heart. Even if it might appear to us that someone has become so hardened against God that they would never return, we do not know what is going on inside that person. Jesus said he came to seek and save the lost. That is what we do know. If someone seems lost, then he or she is precisely the kind of person whom Jesus came to save.