1 Beloved brethren, it ought already to be known to you, as sons of the Church, and well instructed in the school of Christ through all the books of our ancient fathers, who wrote the words of God and the great things of God, that their wish was to consult for our good, who were to live at this period, believers in Christ; who, at a seasonable time came unto us, the first time, in humility; at the second, destined to come in exaltation....For thus it is said in the Psalms: “Truth shall flourish out of the earth: and righteousness has looked down from heaven.” Now, therefore, our whole design is, when we hear a Psalm, a Prophet, or the Law, all of which was written before our Lord Jesus Christ came in the flesh, to see Christ there, to understand Christ there. Attend therefore, beloved, to this Psalm, with me, and let us herein seek Christ; certainly He will appear to those who seek Him, who at first appeared to those who sought Him not; and He will not desert those who long for Him, who redeemed those who neglected Him. Behold, the Psalm begins concerning Him: of Him it is said:—
2. “The Lord is King, be the people angry”. For our Lord Jesus Christ began to reign, began to be preached, after He arose from the dead and ascended into heaven, after He had filled His disciples with the confidence of the Holy Spirit, that they should not fear death, which He had already killed in Himself. Our Lord Christ began then to be preached, that they who wished for salvation might believe in Him; and the peoples who worshipped idols were angry. They who worshipped what they had made were angry, because He by whom they were made was declared. He announced, in fact, through His disciples, Himself, who wished them to be converted unto Him by whom they were made, and to be turned away from those things which they had made themselves. They were angry with their Lord in behalf of their idols, they who even if they were angry with their slave on their idol's account, were to be condemned. For their slave was better than their idol: for God made their slave, the carpenter made their idol. They were so angry in their idol's behalf, that they feared not to be angry with their Lord. But the words, “be they angry,” are a prediction, not a command; for in a prophecy it is that this is said, “The Lord is King, be the people angry.” Some good results even from the enraged people: let them be angry, and in their anger let the Martyrs be crowned....You heard when Jeremiah was being read before the reading of the Apostle, if you listened; ye saw therein the times in which we now live. He said, “The gods that have not made the heavens and the earth, let them perish from the earth, and from under the heaven.” He said not, The gods that have not made the heavens and earth, let them perish from the heaven and from the earth; because they never were in heaven: but what did he say? “Let them perish from the earth, and from under the heaven.” As if, while the word earth was repeated, the repetition of the word heaven were wanting (because they never were in heaven): he repeats the earth twice, since it is under heaven. “Let them perish from the earth, and from under the heaven,” from their temples. Consider if this be not now taking place; if in a great measure it has not already happened: for what, or how much, has remained? The idols remained rather in the hearts of the pagans, than in the niches of the temples.
3. “He who sits between the cherubims:” thou dost understand, “He is King: let the earth be stirred up.”...The Cherubim is the seat of God, as the Scripture shows us, a certain exalted heavenly throne, which we see not; but the Word of God knows it, knows it as His own seat: and the Word of God and the Spirit of God has Itself revealed to the servants of God where God sits. Not that God does sit, as does man; but thou, if you dost wish that God sit in you, if you will be good, shall be the seat of God; for thus is it written, “The soul of the righteous is the seat of wisdom.” For a throne is in our language called a seat. For some, conversant with the Hebrew tongue, have interpreted cherubim in the Latin language (for it is a Hebrew term) by the words, fullness of knowledge. Therefore, because God surpasses all knowledge, He is said to sit above the fullness of knowledge. Let there be therefore in you fullness of knowledge, and even you shall be the throne of God....He knows all things: for our hairs are numbered before God. But the fullness of knowledge which He willed man to know is different from this; the knowledge which He willed you to have, pertains to the law of God. And who can, you may perhaps say unto me, perfectly know the Law, so that he may have within himself the fullness of the knowledge of the Law, and be able to be the seat of God? Be not disturbed; it is briefly told you what you have, if you dost wish to have the fullness of knowledge, and to become the throne of God: for the Apostle says, “Love is the fulfilling of the Law.” What follows then? You have lost the whole of your excuse. Ask your heart; see whether it has love. If there be love there, there is the fulfilment of the Law there also; already God dwells in you, you have become the throne of God. “Be the people angry;” what can the angry people do against him who has become the throne of God? You give heed unto them who rage against you: Who is it that sits within you, you give not heed. You have become a heaven, and do you fear the earth? For the Scripture says in another passage, that the Lord our God does declare, “The heaven is My throne.” If therefore even thou by having the fullness of knowledge, and by having love, hast been made the throne of God, you have become a heaven. For this heaven which we look up to with these eyes of ours, is not very precious before God. Holy souls are the heaven of God; the minds of the Angels, and all the minds of His servants, are the heaven of God.
4. “The Lord is great in Sion, and high above all people”....He whom I spoke to you of as above the Cherubims, is great in Sion. Ask thou now, what is Sion? We know Sion to be the city of God. The city of Jerusalem is called Sion; and is so called according to a certain interpretation, for that Sion signifies watching, that is, sight and contemplation; for to watch is to look forward to, or gaze upon, or strain the eyes to see. Now every soul is a Sion, if it tries to see that light which is to be seen. For if it shall have gazed upon a light of its own, it is darkened; if upon His, it is enlightened. But, now that it is clear that Sion is the city of God; what is the city of God, but the Holy Church? For men who love one another, and who love their God who dwells in them, constitute a city unto God. Because a city is held together by some law; their very law is Love; and that very Love is God: for openly it is written, “God is Love.” He therefore who is full of Love, is full of God; and many, full of love, constitute a city full of God. That city of God is called Sion; the Church therefore is Sion. In it God is great....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)