Theophylact of Ohrid

But when they see that He performs undeniable miracles, and yet blaspheme the Holy Spirit, that is, the miraculous works proceeding from the Holy Spirit, then how will they receive forgiveness if they do not repent? When they were scandalized by the flesh of Christ, in that case, even if they did not repent, they will be forgiven as people who were led astray; but when they saw Him performing the works of God and still blasphemed, how will they be forgiven if they remain unrepentant?

Commentary on Mark ↗

Augustine of Hippo

Or else impenitence itself is the blasphemy against the Holy Ghost which hath no remission. For either in his thought or by his tongue, he speaks a word against the Holy Ghost the forgiver of sins, who treasures up for himself an impenitent heart. …

Catena Aurea by Aquinas ↗

Bede

Whoever blasphemes against the Holy Spirit, has no forgiveness forever, but is guilty of an eternal sin. Therefore, whoever understandingly and manifestly denies the works of God, spurred by envy, calumniates, and says that Christ, the Word of God, and the works of the Holy Spirit are of Beelzebub, to him it will not be forgiven neither in this age nor in the future. …

On the Gospel of Mark ↗