The fourth reason why the place and state of the saints is called the kingdom of heaven — and the most powerful reason — is that all the saints in heaven are kings, and that all the conditions of kingship apply most aptly to them. For although all the saints in heaven serve God, as is said in Revelation, yet at the same time they also reign (Rev. 22:5); for in the same book and the same chapter where it is said, "His servants shall serve Him," a little further on it is said, "and they shall reign for ever and ever." Nor will all the saints merely serve and reign at the same time; they can also be called at once servants and sons. For thus God speaks in Revelation: "He that shall overcome shall possess these things, and I will be his God, and he shall be My son." (Rev. 21:7) Wherefore, just as the same persons can be both servants and sons, so too can they be both servants and kings: for they are servants because they were created by God, and owe obedience to Him from whom they receive their being, and life, and all things; nor does David except anything created when he says, "All things serve You." (Ps. 118:91) Yet at the same time they can be sons of God, since they have been reborn of God through water and the Holy Spirit (John 3:5); and they can likewise be kings, to whom the royal dignity is communicated by the very King of kings, who therefore in the same Revelation is called "King of kings and Lord of lords." (Rev. 19:16) Someone will perhaps say that it is not difficult for a man to be at once a king of the earth and a servant of God, in the way the Psalm says: "And now, O kings, understand; be instructed, you who judge the earth; serve the Lord in fear, and rejoice in Him with trembling." (Ps. 2:10-11) But to be a king of the kingdom of heaven and a servant of the King of heaven — who can grasp or believe this? And yet so it is, and faith grasps this and believes it. The just, therefore, in the kingdom of their Father will themselves also be kings of the kingdom of heaven, because they will be sharers in that royal dignity and power and wealth and the other goods that are in the kingdom of heaven. This the Holy Spirit plainly declares in three principal places of Holy Scripture. One place is in the Gospel of St. Matthew: "Blessed are the poor in spirit, for theirs is the kingdom of heaven." (Matt. 5:3) Another in the same Gospel: "Come, you blessed of My Father, possess the kingdom prepared for you from the foundation of the world." (Matt. 25:34) The third in Revelation: "To him that shall overcome I will grant to sit with Me on My throne, as I also have overcome and have sat down with My Father on His throne." (Rev. 3:21) What can be said more plainly? We have the kingdom of heaven promised to us; we have the possession of that same kingdom to be assigned to us on the day of judgment; we have a seat on the royal throne of the Son of God and of His Father, the eternal King. What is this but a sharing in that same kingdom of heaven which God possesses from eternity? Add the testimony of St. Paul: "If we suffer," he says, "we shall also reign with Him." (2 Tim. 2:12) And of St. John at the beginning of Revelation: "I, John, your brother and sharer in tribulation and in the kingdom." (Rev. 1:9) And of St. James in his Epistle: "God," he says, "has chosen the poor in this world, rich in faith and heirs of the kingdom which God has promised to those who love Him." (Jas. 2:5) Nor is the kingdom of heaven diminished because it is shared by many — indeed nearly innumerable — angels and men; for the kingdom of heaven is not like the kingdoms of the earth, which do not suffer a sharer, and which, if they are divided into parts, are diminished by the division and at last are wholly consumed. Not such, I say, is the kingdom of heaven; rather, the whole of it is possessed by all, and the whole by each one, undiminished — just as the same sun is seen whole by each and whole by all, and itself in turn warms and enlightens each no less than all. This will be more easily understood when the goods of the kingdom of heaven have been explained. But first the conditions or qualities required in kings must be explained, so that no one may doubt that the saints and the blessed in heaven are not without reason called kings, and kings of the kingdom of heaven.
There are two qualities especially necessary for kings: wisdom and justice. But with wisdom Scripture joins prudence and counsel and all that pertains to understanding; with justice it joins mercy, clemency, and the other virtues that adorn and perfect the will. Thus wisdom is required so that the king may know; justice, so that he may will to govern his subjects well. Therefore Solomon, admonished by God at the beginning of his reign to ask for whatever he wished, asked for wisdom, which is the foremost of the good qualities required in kings; and his petition pleased God, as is clear from the third Book of Kings, and so he obtained what he asked. Would that he had asked for justice as well; perhaps he would not have fallen into so many crimes. (1 Kgs. 3) More rightly does David speak in the Psalm in which he prays for blessings on his son Solomon: "Give Your judgment to the king, O God, and Your justice to the king's son." (Ps. 71:1) There he seems to have foreseen that Solomon would ask for wisdom, and therefore he asks for justice and judgment on his behalf — things that cannot exist without wisdom, whereas wisdom can exist without justice, at least a partial and imperfect wisdom. The Book of Wisdom also, which was written expressly for the instruction of kings, says thus: "Love justice, you who judge the earth." (Wis. 1:1) And it begins with justice, because it is not only necessary in itself for kings, but is also a disposition toward wisdom; for a little later it adds: "For wisdom will not enter into a malicious soul." Finally — to pass over many other things — Jeremiah, foretelling the virtues of Christ the eternal King, says: "Behold, the days come, says the Lord, and I will raise up to David a just branch; and a king shall reign and be wise, and shall execute judgment and justice in the earth." (Jer. 23:5) Truly, therefore, wisdom and justice are the dower-gifts required in kings.
Now indeed, it is beyond controversy that all the saints who are in heaven, even though many of them were perhaps unskilled and unlearned while on earth, possess outstanding wisdom and the eminent virtue of justice, so that they could worthily be made kings of any kingdom whatever. For there is no one among the saints in heaven who does not see the very essence of God, which is the first cause of all things; and therefore they draw from the fount of uncreated wisdom a wisdom so great as neither Solomon nor any mortal man ever possessed, except our Lord Jesus Christ, who even in the time of His mortality saw God, and in whom were all the treasures of the wisdom and knowledge of God (Col. 2:3). Moreover, in proportion to their wisdom, a full measure of justice is also given to all the saints, so that henceforth they neither will nor can sin; for so speaks St. Augustine in the book On Rebuke and Grace: "The first liberty of the will was to be able not to sin; the last will be much greater: not to be able to sin." (On Rebuke and Grace, ch. 11.) But he who cannot sin cannot be unjust either; and since perfect charity is perfect justice, as the same St. Augustine affirms at the end of the book On Nature and Grace, he who cannot but love God with the highest and most perfect love likewise cannot but possess the highest and most perfect justice (On Nature and Grace, last chapter). But those who see God, the highest and pure and infinite good, certainly cannot be turned away from Him, nor can they fail to love Him always with the most ardent love; whence it comes about that all the saints in heaven are always perfectly wise and perfectly just, and therefore ever most fit to reign.
Arise, therefore, O Christian soul, and ascend in mind as far as you can, and consider what a good thing it is to reign with God; and, to pass over all other things for now, pierce the very heavens with the wings of contemplation and behold that lofty throne of which the Savior says: To him that shall overcome, I will give to sit with Me on My throne, as I also have overcome and am seated with My Father on His throne (Rev. 3:21). For how great will that glory be, for a just soul to be placed upon the very throne of Christ and of God before the infinite multitude of the angels, and by the just judgment of God to be proclaimed the conqueror of the world and of the rulers of the world and of all invisible powers? And with how great a joy will that same soul exult, when it sees itself delivered from every danger and labor, triumphing most happily over all its enemies? And what will remain for it to desire further, when it has been made a sharer in all the goods of its Lord, even to fellowship in His throne and kingdom? O how cheerfully do they fight on earth, and how easily do they bear all adversities for Christ, who by a living faith and a sure hope behold with the eye of the mind such sublime honors in heaven!