Unfortunately, even though "thus saith the Lord" is equivalent to what is written the the Holy Scriptures, there are many who will not believe the truth but persist in their lies.
Take John 1:1 as an example.
In the beginning was the Word, and the Word was with God, and the Word was God.
Did John write by Divine inspiration? Absolutely
Did he reveal that there are two divine Persons in the Godhead? Absolutely
Did he plainly state that "the Word is God"? Absolutely
Yet we still have naysayers claiming that Jesus is NOT God.
And the same applies to the Holy Spirit. We still have naysayers claiming that the Holy Spirit is NOT the third Person of the Trinity, even though Matthew 28:19 is authentic Scripture, and includes the Holy Ghost as one one of Persons within the Godhead.
Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost.
Jesus spoke of blaspheming the Holy Ghost, and it is only God who can be blasphemed.
Wherefore I say unto you, All manner of sin and blasphemy shall be forgiven unto men: but the blasphemy against the Holy Ghost shall not be forgiven unto men.