In Mark 3 it talks about the blasphemy of the Holy Spirit and we do not understand what that means. Maybe you can explain that so we can understand.
The passage you are referring to says: "Assuredly, I say to you, all sins will be forgiven the sons of men, and whatever blasphemies they may utter; but he who blasphemes against the Holy Spirit never has forgiveness, but is subject to eternal condemnation" (Mark 3:28-29).
First, we need a good definition of what exactly is blaspheme. For that, we will go back to Numbers 15:30-31. "But the person who does anything defiantly, whether he is native or an alien, that one is blaspheming the LORD; and that person shall be cut off from among his people. Because he has despised the word of the LORD and has broken His commandment, that person shall be completely cut off; his guilt will be on him." Hence, we learn that God's definition of blaspheme is acting in defiance of the Lord and His commandments. In other words, blaspheme is willfully sinning when you know full well that it is wrong. But the defiance involves a particular type of sin: slandering God's reputation before other people. Thus, blasphemy is a willful attempt to ruin God's reputation, even though you know what you are saying is wrong.
Korah and his followers illustrate this in Numbers 16. They knew that God made Moses the leader and Aaron his High Priest; yet they believe they had equal rights to talk with God as Moses did. Even when warned, they stubbornly persisted in asserting what they believed to be their rights. In doing so, they were claiming that God made a mistake in selecting Moses and Aaron. For that, they died in a dramatic fashion.
There is something about defiant sin that makes it hard to let go. In the New Testament, it is referred to as willful sin. "For if we sin willfully after we have received the knowledge of the truth, there no longer remains a sacrifice for sins, but a certain fearful expectation of judgment, and fiery indignation which will devour the adversaries" (Hebrews 10:26-27). The reason is that there is only one route to salvation and that is through humble submission to God. "For it is impossible for those who were once enlightened, and have tasted the heavenly gift, and have become partakers of the Holy Spirit, and have tasted the good word of God and the powers of the age to come, if they fall away, to renew them again to repentance, since they crucify again for themselves the Son of God, and put Him to an open shame" (Hebrews 6:4-6).
Blasphemy is the willful rejection of God after a person has learned better and a desire to have others also reject God. Jesus told his audience that they could reject him and his teachings, but if they blasphemed the Holy Spirit - rejected the Spirit's teaching and slander His work - it would not be forgiven (Luke 12:10; Matthew 12:31-32; Mark 3:28-30). It was the work of the Holy Spirit to confirm the teaching of God's word (Mark 16:20; Hebrews 2:3-4). If a man rejects the proof offered, how can the Bible be proven? The Holy Spirit also delivered the word of God using the apostles as the vehicle to write down the words he delivered (John 14:25-26; 16:12-14; I Corinthians 2:12-13). If a man willfully rejects the work of the Holy Spirit - the Bible - and rejects the proof that His work is true - the miracles done - then what hope is there for that man to be saved? We are not talking about initial disbelief that fades as the evidence mounts up before them. We are talking about someone who sees the evidence, understands the significance of the evidence, but then purposely chooses to go against God anyway.
This is why Jesus was scolding his audience. They saw the miracle. Because it was done in their presence, they could not deny the result. Instead of accepting it as proof that the Spirit was working through Jesus, they chose to state what they knew could not be true -- that the miracle was done by the power of Satan. Such willful defiance of the Spirit and slander of His work demonstrated that they could not be saved. They would not turn from their sin. No amount of evidence would ever persuade them. Therefore, they could not be forgiven, not that God would refuse to forgive them, but because they would not ever return to the God they rejected.
It is not that God wants to punish a person. God desires that everyone would be saved (II Peter 3:9). However, there comes a time to acknowledge that some people will reject God's gift of salvation and without that gift, there is no hope.