10 Nor, because I called Ruth blessed, Anna more blessed, in that the former married twice, the latter, being soon widowed of her one husband, so lived long, do you straightway also think that you are better than Ruth. Forsooth different in the times of the Prophets was the dispensation of holy females, whom obedience, not lust, forced to marry, for the propagation of the people of God, that in them Prophets of Christ might be sent beforehand; whereas the People itself also, by those things which in figure happened among them, whether in the case of those who knew, or in the case of those who knew not those things, was nothing else than a Prophet of Christ, of whom should be born the Flesh also of Christ.
In order therefore for the propagation of that people, he was accounted accursed by sentence of the Law, whoso raised not up seed in Israel. Whence also holy women were kindled, not by lust of sensual intercourse, but by piety of bearing; so that we most rightly believe of them that they would not have sought sensual intercourse, in case a family could have come by any other means. And to the husbands was allowed the use of several wives living; and that the cause of this was not lust of the flesh, but forethought of begetting, is shown by the fact, that, as it was lawful for holy men to have several wives living, it was not likewise lawful for holy women to have intercourse with several husbands living; in that they would be by so much the baser, by how much the more they sought what would not add to their fruitfulness.
Wherefore holy Ruth, not having seed such as at that time was necessary in Israel, on the death of her husband sought another of whom to have it. Therefore than this one twice married, Anna once married a widow was on this account more blessed, in that she attained also to be a prophetess of Christ; concerning whom we are to believe, that, although she had no sons, (which indeed Scripture by keeping silence has left uncertain,) yet, had she by that Spirit foreseen that Christ would immediately come of a virgin, by Which she was enabled to recognize Him even as a child: whence, with good reason, even without sons, (that is, assuming she had none,) she refused a second marriage: in that she knew that now was the time wherein Christ were better served, not by duty of bearing, but by zeal of containing: not by fruitfulness of married womb, but by chastity of widowed conduct.
But if Ruth also was aware that by her flesh was propagated a seed, whereof Christ should hereafter have flesh, and by marrying set forth her ministering to this knowledge, I dare not any longer say that the widowhood of Anna was more blessed than her fruitfulness.
Source: On the Good of Widowhood (New Advent)