4 Let us now come to the words, “Your wife”: it is said unto Christ. His wife, therefore, is the Church: His Church, His wife, we ourselves are. “As a fruitful vineyard.” But in whom is the vineyard fruitful? For we see many barren ones entering those walls; we see that many intemperate, usurious persons, slave dealers, enter these walls, and such as resort to fortune-tellers, go to enchanters and enchantresses when they have a headache. Is this the fruitfulness of the vine? Is this the fecundity of the wife? It is not. These are thorns, but the vineyard is not everywhere thorny. It has a certain fruitfulness, and is a fruitful vine; but in whom? “Upon the sides of your house.” Not all are called the sides of the house. For I ask what are the sides. What shall I say? Are they walls, strong stones, as it were? If he were speaking of this bodily tenement, we should perhaps understand this by sides. We mean by the sides of the house, those who cling unto Christ....
5. “Your children.” The wife and the children are the same. In these carnal marriages and wedlocks, the wife is one, the children other: in the Church, she who is the wife, is the children also. For the Apostles belonged to the Church, and were among the members of the Church. They were therefore in His wife, and were His wife according to their own portion which they held in His members. Why then is it said concerning them, “When the Bridegroom shall be taken from them, then shall the children of the Bridegroom fast”? She who is the wife, then, is the children also. I speak a wonderful thing, my brethren. In the words of the Lord, we find the Church to be both His brethren, and His sisters, and His mother....For Mary was among the sides of His House, and His relatives coming of the kindred of the Virgin Mary, who believed on Him, were among the sides of His House; not in respect of their carnal consanguinity, but inasmuch as they heard the Word of God, and obeyed it....He added; “For whosoever shall do the will of My Father which is in heaven, the same is My brother, and sister, and mother.” “Brother,” perhaps, on account of the male sex whom the Church has: “sister,” on account of the women whom Christ has here in His members. How “mother,” save that Christ Himself is in those Christians, whom the Church daily brings forth Christians through baptism? In those therefore in whom you understand the wife, in them you understand the mother, in them the children.
6....Such children ought therefore to be “around” the Lord's “table, like olive-branches.” A complete Vine it is, a great bliss: who would now refuse to be there? When you see any blasphemer have a wife, children, grandchildren, and yourself perchance without them, envy them not; discern that the promise has been fulfilled in you also, but spiritually. If therefore we have, why have we? Because we fear the Lord. “Lo, thus shall the man be blessed that fears the Lord”. He is the man, who is also the men; and the men are one man; because many are one, because Christ is One.
7. “The Lord from out of Sion bless you: and may thou see you good things that are of Jerusalem”. Even to the birds was it said, “Be fruitful and multiply.” Do you wish to hold as a great blessing what was given unto birds? Who can be ignorant, that it was given indeed by the voice of God? But use these goods, if you receive them; and rather think how you may nourish those who have been born, than that others may be born. For it is not happiness to have children, but to have good ones. Labour in the task of nourishing them, if they be born; but if they be not born, give thanks unto God....Your children are infants: thou dost caress the infants: the infants caress you: do they abide thus? But you wish they may grow, you wish that their age may increase. But consider that when one age comes, another dies. When boyhood comes, infancy dies; when youth comes, boyhood dies: when manhood comes, youth dies; when old age comes, manhood dies: when death comes, all age dies. As many successions of ages as you wish for, so many deaths of ages do you wish for. These things therefore “are” not. Finally, are children born unto you to share life with you on earth, or rather to shut you out and to succeed you? Rejoicest thou in those born to exclude you? Boys when born speak somewhat like this to their parents: “Now then, begin to think of removing hence, let us too play our parts on the stage.” For the whole life of temptation in the human race is a stage play; for it is said, “Every man living is altogether vanity.” Nevertheless, if we rejoice in children who will succeed us; how much must we rejoice in children with whom we shall remain, and in that Father for whom we are born, who will not die, but that we may evermore live with Him? These are the good things of Jerusalem: for they “are.” And how long shall I see the good things of Jerusalem? “All your life long.” If your life be for ever, you will see the good things of Jerusalem for evermore....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)