31 I will speak freely, and although you screw your mouths, pull your hair, stamp your feet, and take up stones like the Jews, I will openly confess the faith of the Church. The reality of a resurrection without flesh and bones, without blood and members, is unintelligible. Where there are flesh and bones, where there are blood and members, there must of necessity be diversity of sex. Where there is diversity of sex, there John is John, Mary is Mary. You need not fear the marriage of those who, even before death, lived in their own sex without discharging the functions of sex.
When it is said, “In that day they shall neither marry, nor be given in marriage,” the words refer to those who can marry, and yet will not do so. For no one says of the angels, “They shall not marry, nor be given in marriage.” I never heard of a marriage being celebrated among the spiritual virtues in heaven: but where there is sex, there you have man and woman. Hence it is that, although you were reluctant, you were compelled by the truth to confess that, “A man must either be crowned in the body because he lived a pure and upright life, or be condemned in the body, because he was the slave of pleasure and iniquity.”
Substitute flesh for body, and you have not denied the existence of male and female. Who can have any glory from a life of chastity if we have no sex which would make unchastity possible? Who ever crowned a stone for continuing a virgin? Likeness to the angels is promised us, that is, the blessedness of their angelic existence without flesh and sex will be bestowed on us in our flesh and with our sex. I am simple enough so to believe, and so know how to confess that sex can exist without the functions of the senses; that it is thus that men rise, and that it is thus that they are made equal to the angels.
Nor will the resurrection of the members all at once seem superfluous, because they are to have no office, since, while we are still in this life, we strive not to perform the works of the members. Moreover, likeness to the angels does not imply a changing of men into angels, but their growth in immortality and glory.
Source: To Pammachius Against John of Jerusalem (New Advent)