That they who deny the Spirit are transgressors.
27. “Who has woe? Who has sorrow?” For whom is distress and darkness? For whom eternal doom? Is it not for the transgressors? For them that deny the faith? And what is the proof of their denial? Is it not that they have set at naught their own confessions? And when and what did they confess? Belief in the Father and in the Son and in the Holy Ghost, when they renounced the devil and his angels, and uttered those saving words. What fit title then for them has been discovered, for the children of light to use? Are they not addressed as transgressors, as having violated the covenant of their salvation? What am I to call the denial of God? What the denial of Christ? What but transgressions? And to him who denies the Spirit, what title do you wish me to apply? Must it not be the same, inasmuch as he has broken his covenant with God? And when the confession of faith in Him secures the blessing of true religion. and its denial subjects men to the doom of godlessness, is it not a fearful thing for them to set the confession at naught, not through fear of fire, or sword, or cross, or scourge, or wheel, or rack, but merely led astray by the sophistry and seductions of the pneumatomachi? I testify to every man who is confessing Christ and denying God, that Christ will profit him nothing; to every man that calls upon God but rejects the Son, that his faith is vain; to every man that sets aside the Spirit, that his faith in the Father and the Son will be useless, for he cannot even hold it without the presence of the Spirit. For he who does not believe the Spirit does not believe in the Son, and he who has not believed in the Son does not believe in the Father. For none “can say that Jesus is the Lord but by the Holy Ghost,” and “No man has seen God at any time, but the only begotten God which is in the bosom of the Father, he has declared him.”
Such an one has neither part nor lot in the true worship; for it is impossible to worship the Son, save by the Holy Ghost; impossible to call upon the Father, save by the Spirit of adoption.
Source: De Spiritu Sancto (New Advent)