Had spoken one word - One solemn declaration, reminding them that it was the characteristic of the nation to reject the testimony of God, and that it was to be expected. It was the last warning which we know Paul to have delivered to his countrymen the Jews.
Well spake - Or he spoke the truth; he justly described the character of the Jewish people. The passage here quoted was as applicable in the time of Paul as of Isaiah.
The Holy Ghost - A full proof of the inspiration of Isaiah.
By Esaias - By Isaiah, Isaiah 6:9-10.