The Son Himself does not judge or punish without the Spirit, so that the same Spirit is called the Sword of the Word. But inasmuch as the Word is in turn called the Sword of the Spirit, the highest unity of power is thereby recognized in each.
44. But what should we say of the other points? We have heard that the Lord Jesus not only judges in the Spirit but punishes also. For neither would He punish Antichrist, whom, as we read, “the Lord Jesus shall slay with the Spirit of His mouth,” unless He had before judged of his deserts. Yet here is not a grace received, but the unity remains undivided, since neither can Christ be without the Spirit, nor the Spirit without Christ. For the unity of the divine nature cannot be divided.
45. And since that instance comes before us, that the Lord Jesus shall slay with the Spirit of His mouth, the Spirit is understood to be as it were the Sword of the Word. Lastly, in the Gospel also the Lord Jesus Himself says: “I came not to send peace but a sword.” For He came that He might give the Spirit; and so there is in His mouth a two-edged sword, which is in truth the grace of the Spirit. So the Spirit is the Sword of the Word.
46. And that you may know that there is no inequality but unity of nature, the Word also is the Sword of the Holy Spirit, for it is written: “Taking the shield of faith, wherewith you may be able to quench all the fiery darts of the wicked one. And take the helmet of Salvation, and the sword of the Spirit, which is the Word of God.”
47. Since, then, the Sword of the Word is the Holy Spirit, and the Sword of the Holy Spirit is the Word of God, there is certainly in Them oneness of power.
Source: On the Holy Spirit (New Advent)