All manner of sin and blasphemy shall be be forgiven unto men: but the blasphemy against the Holy Ghost shall NOT be forgiven unto men. And whosoever speaketh a word against the Son of man, it shall be forgiven him: but whosoever speaketh against the Holy Ghost, it shall NOT be forgiven him, neither in this world, neither in the world to come.
This is powerful warning of Jesus Christ not to speak against the Holy Spirit. We have no explanation why blasphemy against the Holy Spirit is unforgivable offense against God, the highest Being of all the universe. We just rely on what Jesus said about offending the Holy Spirit by way of blasphemy which is mainly speaking against the integrity of the person of the Holy Spirit.
The Holy Spirit is a vey sensitive Person. What He hears become part of His Person. Our prayers and petitions are important to Him. Maybe as important as the words of Jesus to Him. He respects the words of Jesus He hears, which are forever recorded in His mind to be relayed to every believer during their time of remembering.
The Holy Spirit is a serious Person. He takes very word of Jesus seriously. The promises of Jesus to Him are not meant to be jokes or to be taken lightly. Though He is a serious Person, He is a joyful Person for the fruit of the Spirit is joy. The Spirit of God is well of joy for every believer who trusted Jesus Christ and His words.
The Holy Spirit is pure and sinless Person. Jesus called Him, “Holy”so He must be a perfect person without any flaws or imperfections. He is a totally complete Person, self-sufficient divine Being. We need Him more than He needed us. To speak against Him is detrimental to our cause. We should think twice before we open our mouths in disrespect against the Holy One.
Still at closing, we don’t have an answer why the Holy Ghost chooses not to forgive the sin of blasphemy against the most Holy One.