Objection 1. It would seem that the judicial power does not correspond to voluntary poverty. For it was promised to none but the twelve apostles (Matthew 19:28): "You shall sit on twelve seats, judging," etc. Since then those who are voluntarily poor are not all apostles, it would seem that the judicial power is not competent to all.
Objection 2. Further, to offer sacrifice to God of one's own body is more than to do so of outward things. Now martyrs and also virgins offer sacrifice to God of their own body. whereas the voluntarily poor offer sacrifice of outward things. Therefore the sublimity of the judicial power is more in keeping with martyrs and virgins than with those who are voluntarily poor.
Objection 3. Further, it is written (John 5:45): "There is one that accuseth you, Moses in whom you trust--because you believe not his voice," according to a gloss, and (John 12:48): "The word that I have spoken shall judge him in the last day." Therefore the fact that a man propounds a law, or exhorts men by word to lead a good life, gives him the right to judge those who scorn his utterances. But this belongs to doctors. Therefore it is more competent to doctors than to those who are poor voluntarily.
Objection 4. Further, Christ through being judged unjustly merited as man to be judge of all in His human nature [Cf. III, 59, 6], according to John 5:27, "He hath given Him power to do judgment, because He is the Son of man." Now those who suffer persecution for justice' sake are judged unjustly. Therefore the judicial power is competent to them rather than to the voluntarily poor.
Objection 5. Further, a superior is not judged by his inferior. Now many who will have made lawful use of riches will have greater merit than many of the voluntarily poor. Therefore the voluntarily poor will not judge where those are to be judged.
On the contrary, It is written (Job 36:6): "He saveth not the wicked, and He giveth judgment to the poor."
Further, a gloss on Matthew 19:28, "You who have left all things' [Vulgate: 'You who have followed Me']" says: "Those who left all things and followed God will be the judges; those who made right use of what they had lawfully will be judged," and thus the same conclusion follows as before.
I answer that, The judicial power is due especially to poverty on three counts. First, by reason of congruity, since voluntary poverty belongs to those who despise all the things of the world and cleave to Christ alone. Consequently there is nothing in them to turn away their judgment from justice, so that they are rendered competent to be judges as loving the truth of justice above all things. Secondly, by reason of merit, since exaltation corresponds by way of merit to humility. Now of all the things that make man contemptible in this world humility is the chief: and for this reason the excellence of judicial power is promised to the poor, so that he who humbles himself for Christ's sake shall be exalted. Thirdly, because poverty disposes a man to the aforesaid manner of judging. For the reason why one of the saints will be said to judge as stated above [Cf. 1], is that he will have the heart instructed in all Divine truth which he will be thus able to make known to others. Now in the advancement to perfection, the first thing that occurs to be renounced is external wealth, because this is the last thing of all to be acquired. And that which is last in the order of generation is the first in the order of destruction: wherefore among the beatitudes whereby we advance to perfection, the first place is given to poverty. Thus judicial power corresponds to poverty, in so far as this is the disposition to the aforesaid perfection. Hence also it is that this same power is not promised to all who are voluntarily poor, but to those who leave all and follow Christ in accordance with the perfection of life.
Reply to Objection 1. According to Augustine (De Civ. Dei xx), "we must not imagine that because He says that they will sit on twelve seats only twelve men will judge with Him. else since we read that Matthias was appointed apostle in the place of the traitor Judas, Paul who worked more than the rest will have nowhere to sit as judge." Hence "the number twelve," as he states (De Civ. Dei xx), "signifies the whole multitude of those who will judge, because the two parts of seven, namely three and four, being multiplied together make twelve." Moreover twelve is a perfect number, being the double of six, which is a perfect number.
Or, speaking literally, He spoke to the twelve apostles in whose person he made this promise to all who follow them.
Reply to Objection 2. Virginity and martyrdom do not dispose man to retain the precepts of Divine justice in his heart in the same degree as poverty does: even so, on the other hand, outward riches choke the word of God by the cares which they entail (Luke 8:14). Or we may reply that poverty does not suffice alone to merit judicial power, but is the fundamental part of that perfection to which the judicial power corresponds. Wherefore among those things regarding perfection which follow after poverty we may reckon both virginity and martyrdom and all the works of perfection: yet they do not rank as high as poverty, since the beginning of a thing is its chief part.
Reply to Objection 3. He who propounded the law or urged men to good will judge, in the causal (Cf. 1) sense, because others will be judged in reference to the words he has uttered or propounded. Hence the judicial power does not properly correspond to preaching or teaching. or we may reply that, as some say, three things are requisite for the judicial power; first, that one renounce temporal cares, lest the mind be hindered from the contemplation of wisdom; secondly that one possess Divine justice by way of habit both as to knowledge and as to observance; thirdly that one should have taught others this same justice; and this teaching will be the perfection whereby a man merits to have judicial power.
Reply to Objection 4. Christ humbled Himself in that He was judged unjustly; for "He was offered because it was His own will" (Isaiah 53:7): and by His humility He merited His exaltation to judicial power, since all things are made subject to Him (Philippians 2:8-9). Hence, judicial power is more due to them who humble themselves of their own will by renouncing temporal goods, on account of which men are honored by worldlings, than to those who are humbled by others.
Reply to Objection 5. An inferior cannot judge a superior by his own authority, but he can do so by the authority of a superior, as in the case of a judge-delegate. Hence it is not unfitting that it be granted to the poor as an accidental reward to judge others, even those who have higher merit in respect of the essential reward.
Source: Summa Theologica (New Advent)