7 But the saints who “exult in glory,” no need is there for us to say how they exult: just hear the verse of the Psalm which follows: “The saints shall exult in glory, they shall rejoice in their beds:” not in theatres, or amphitheatres, or circuses, or follies, or market places, but “in their chambers.” What is, “in their chambers”? In their hearts. Hear the Apostle Paul exulting in his closet: “For this is our glory, the testimony of our conscience.” On the other hand, there is reason to fear lest any be pleasing to himself, and so seem to be proud, and boast of his conscience. For every one ought to exult with fear, for that wherein he exults is God's gift, not his own desert. For there be many that please themselves, and think themselves righteous; and there is another passage which goes against them, which says, “Who shall boast that he has a clean heart, and that he is pure from sin?” There is then, so to speak, a limit to glorying in our conscience, namely, to know that your faith is sincere, your hope sure, your love without dissimulation. “The exultations of God are in their mouths”. In such wise shall they “rejoice in their closets,” as not to attribute to themselves that they are good, but praise Him from whom they have what they are, by whom they are called to attain to what they are not, and from whom they hope for perfection, to whom they give thanks, because He has begun.
8. “And swords sharpened on both sides in their hands.” This sort of weapon contains a great mystical meaning, in that it is sharp on both sides. By “swords sharpened on both sides,” we understand the Word of the Lord: it is one sword, but therefore are they called many, because there are many mouths and many tongues of the saints. How is it two edged? It speaks of things temporal, it speaks also of things eternal. In both cases it proves what it says, and him whom it strikes, it severs from the world. Is not this the sword whereof the Lord said, “I am not come to send peace upon earth, but a sword”? Observe how He came to divide, how He came to sever. He divides the saints, He divides the ungodly, He severs from you that which hinders you. The son wills to serve God, the father wills not: the sword comes, the Word of God comes, and severs the son from the father....Wherefore then is it in their hands, not in their tongues? “And swords,” it says, “sharpened on both sides in their hands.” By “in their hands,” he means in power. They received then the word of God in power, to speak where they would, to whom they would, neither to fear power, nor to despise poverty. For they had in their hands a sword; where they would they brandished it, handled it, smote with it: and all this was in the power of the preachers. For if the Word be not in their hands, why is it written, “The Word of the Lord was put in the hand of the Prophet Haggai”? Surely, brethren, God set not His Word in His fingers. What is meant by, “was put in his hand”? It was put into his power to preach the Word of the Lord. Lastly, we can understand these “hands” in another way also. For they who spoke had the word of God in their tongues, they who wrote, in their hands.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)