For it is reasonable to believe that she, who brought forth "the Only-Begotten of the Father full of grace and truth," received greater privileges of grace than all others: hence we read (Lk. 1:28) that the angel addressed her in the words: "Hail full of grace!"
Moreover, it is to be observed that it was granted, by way of privilege, to others, to be sanctified in the womb; for instance, to Jeremias, to whom it was said (Jer. 1:5): "Before thou camest forth out of the womb, I sanctified thee"; and again, to John the Baptist, of whom it is written (Lk. 1:15): "He shall be filled with the Holy Ghost even from his mother's womb." It is therefore with reason that we believe the Blessed Virgin to have been sanctified before her birth from the womb.
... Objection 2: Further, Augustine says (Ep. ad Dardan.): "The sanctification, by which we become temples of God, is only of those who are born again." But no one is born again, who was not born previously. Therefore the Blessed Virgin was not sanctified before her birth from the womb.
Reply to Objection 2: Augustine speaks according to the common law, by reason of which no one is regenerated by the sacraments, save those who are previously born. But God did not so limit His power to the law of the sacraments, but that He can bestow His grace, by special privilege, on some before they are born from the womb.
Objection 3: Further, whoever is sanctified by grace is cleansed from sin, both original and actual. If, therefore, the Blessed Virgin was sanctified before her birth from the womb, it follows that she was then cleansed from original sin. Now nothing but original sin could hinder her from entering the heavenly kingdom. If therefore she had died then, it seems that she would have entered the gates of heaven. But this was not possible before the Passion of Christ, according to the Apostle (Heb. 10:19): "We have [Vulg.: 'having'] therefore a confidence in the entering into the Holies by His blood." It seems therefore that the Blessed Virgin was not sanctified before her birth from the womb.
... Reply to Objection 3: The Blessed Virgin was sanctified in the womb from original sin, as to the personal stain; but she was not freed from the guilt to which the whole nature is subject, so as to enter into Paradise otherwise than through the Sacrifice of Christ; the same also is to be said of the Holy Fathers who lived before Christ.
ST IIIa Q. 27 — Aquinas 101
Moreover, it is to be observed that it was granted, by way of privilege, to others, to be sanctified in the womb; for instance, to Jeremias, to whom it was said (Jer. 1:5): "Before thou camest forth out of the womb, I sanctified thee"; and again, to John the Baptist, of whom it is written (Lk. 1:15): "He shall be filled with the Holy Ghost even from his mother's womb." It is therefore with reason that we believe the Blessed Virgin to have been sanctified before her birth from the womb.
... Objection 2: Further, Augustine says (Ep. ad Dardan.): "The sanctification, by which we become temples of God, is only of those who are born again." But no one is born again, who was not born previously. Therefore the Blessed Virgin was not sanctified before her birth from the womb.
Reply to Objection 2: Augustine speaks according to the common law, by reason of which no one is regenerated by the sacraments, save those who are previously born. But God did not so limit His power to the law of the sacraments, but that He can bestow His grace, by special privilege, on some before they are born from the womb.
Objection 3: Further, whoever is sanctified by grace is cleansed from sin, both original and actual. If, therefore, the Blessed Virgin was sanctified before her birth from the womb, it follows that she was then cleansed from original sin. Now nothing but original sin could hinder her from entering the heavenly kingdom. If therefore she had died then, it seems that she would have entered the gates of heaven. But this was not possible before the Passion of Christ, according to the Apostle (Heb. 10:19): "We have [Vulg.: 'having'] therefore a confidence in the entering into the Holies by His blood." It seems therefore that the Blessed Virgin was not sanctified before her birth from the womb.
... Reply to Objection 3: The Blessed Virgin was sanctified in the womb from original sin, as to the personal stain; but she was not freed from the guilt to which the whole nature is subject, so as to enter into Paradise otherwise than through the Sacrifice of Christ; the same also is to be said of the Holy Fathers who lived before Christ.
ST IIIa Q. 27 — Aquinas 101