In all three instances of Jesus rebuking with a comment about the unpardonable sin (Matt 12:22; Mark 3:28-29; Luke 12:8-10) it was directed towards a specific group of people who, in slandering Him for His miracles, were instead ignorantly slandering God.

Therefore I say to you, any sin and blasphemy shall be forgiven people, but blasphemy against the Spirit shall not be forgiven. Whoever speaks a word against the Son of Man, it shall be forgiven him; but whoever speaks against the Holy Spirit, it shall not be forgiven him, either in this age or in the age to come. (Matt 12:31-32; Mark 3:28-30; Luke 12:8-10)

The Greek verb "blasphēmeō" and its word group during the first century meant "speak harm" in the context of to bring ill repute or slander; it was profane language, slanderous speech or defamation by which another person was damaged.

Jesus makes a distinction between His person and His works. Despite being the agent of miracles, Jesus credits His work of miracles to "the Spirit" who Jesus teaches is in reality God.

God is spirit, and those who worship Him must worship in spirit and truth. (John 4:24)

As teachers of the Law, the Pharisees were supposed to know God's word especially concerning Moses.

Then Moses said to the Lord, "Please, Lord, I have never been eloquent, neither recently nor in time past, nor since You have spoken to Your servant; for I am slow of speech and slow of tongue." The Lord said to him, "Who has made man's mouth? Or who makes him mute or deaf, or seeing or blind? Is it not I, the Lord? (Ex 4:10-11)

Rather than recognize Jesus as the Son of God because of the miracles that only God could do, the Pharisees accuse Him of being possessed by Satan and doing works by demonic power.

This is in stark contrast to Jesus' name, God's salvation, and His purpose.

But the testimony which I have is greater than the testimony of John; for the works which the Father has given Me to accomplish—the very works that I do—testify about Me, that the Father has sent Me. And the Father who sent Me, He has testified of Me. You have neither heard His voice at any time nor seen His form. You do not have His word abiding in you, for you do not believe Him whom He sent. (John 5:36-38)

For I have come down from heaven, not to do My own will, but the will of Him who sent Me. (John 6:38)

Because of their hard hearts, the Pharisees defamed God by attributing His miracles to Satan and in so doing violated the third commandment, "You shall not take the name of the Lord your God in vain, for the Lord will not leave him unpunished who takes His name in vain." (Ex 20:7)

Then Moses said to God, "Behold, I am going to the sons of Israel, and I will say to them, 'The God of your fathers has sent me to you.' Now they may say to me, 'What is His name?' What shall I say to them?" God said to Moses, "I AM WHO I AM"; and He said, "Thus you shall say to the sons of Israel, 'I AM has sent me to you.'" (Ex 3:13-14)

Hebrew language scholars indicate that grammatical construction of the phrase "I AM WHO I AM" makes the connection between the name YHWH and God's essence Himself. The phrase can be understood as "I AM HE WHO EXISTS."

The name of God is more than just a title, it includes His nature, being, and very character / word.

Jesus' severe rebuke of blaspheming the Holy Spirit, in the manner of the Pharisees who slandered God despite their scholarly knowledge of His word, finds its basis in the violation of His Father's third commandment.

To learn more, see:

The Unpardonable Sin: Blasphemy of the Holy Spirit