24 But concerning what eunuchs speaks God by the prophet Isaiah, unto whom He says that He will give in His house and in His wall a place by name, much better than of sons and daughters, save concerning these, who make themselves eunuchs for the sake of the kingdom of heaven? For for these, whose bodily organ is without strength, so that they cannot beget, (such as are the eunuchs of rich men and of kings,) it is surely enough, when they become Christians, and keep the commands of God, yet have this purpose, that, if they could, they would have wives, to be made equal to the rest of the faithful in the house of God, who are married, who bring up in the fear of God a family which they have lawfully and chastely gotten, teaching their sons to set their hope on God; but not to receive a better place than of sons and daughters.
For it is not of virtue of the soul, but of necessity of the flesh, that they marry not wives. Let who will contend that the Prophet foretold this of those eunuchs who have suffered mutilation of body; that even also helps the cause which we have undertaken. For God has not preferred these eunuchs to such as have no place in His house, but assuredly to those who keep the desert of married life in begetting sons. For, when He says, “I will give unto them a place much better;” He shows that one is also given unto the married, but much inferior.
Therefore, to allow that in the house of God there will be the eunuchs after the flesh spoken of above, who were not in the People of Israel: because we see that these also themselves, whereas they become not Jews, yet become Christians: and that the Prophet spoke not of them, who through purpose of continence seeking not marriage, make themselves eunuchs for the sake of the kingdom of heaven: is any one so madly opposed to the truth as to believe that eunuchs made so in the flesh have a better place than married persons in the house of God, and to contend that persons being of pious purpose continent, chastening the body even unto contempt of marriage, making themselves eunuchs, not in the body, but in the very root of concupiscence, practising an heavenly and angelic life in an earthly mortal state, are on a level with the deserts of the married; and, being a Christian, to gainsay Christ when He praises those who have made themselves eunuchs, not for the sake of this world, but for the sake of the kingdom of heaven, affirming that this is of use for the present life, not for a future?
What else remains for these, save to assert that the kingdom of heaven itself pertains unto this temporal life, wherein we now are? For why should not blind presumption advance even to this madness? And what more full of phrensy than this assertion? For, although at times the Church, even that which is at this time, is called the kingdom of heaven; certainly it is so called for this end, because it is being gathered together for a future and eternal life. Although, therefore, it have the promise of the present, and of a future life, yet in all its good works it looks not to “the things that are seen, but to what are not seen. For what are seen are temporal; but what are not seen, are eternal.”
Source: On Holy Virginity (New Advent)