Thomas Aquinas

“ Nevertheless, before animation the body of the Blessed Virgin, being seminally descended from Adam, was such that it would have been the means of transmitting the taint of original sin to the rational soul at the very first instant of animation, unless the grace of the Redeemer intervened and sanctified her soul "in that self-same instant," thus redeeming her and preventing her from contracting the guilt of original sin.
Why, then, does St. Thomas say that because the Blessed Virgin was not sanctified before animation, therefore she could be sanctified only after animation? ”

“ But both can be applied to Him as man. Because, as man, He is distant both from God, by nature, and from man by dignity of both grace and glory. Again, it belongs to Him, as man, to unite men to God, by communicating to men both precepts and gifts, and by offering satisfaction and prayers to God for men. And therefore He is most truly called Mediator, as man. ”

“ Further, just as Christ, as God, has a common nature with the Father and the Holy Ghost; so, as man, He has a common nature with men. But for the reason that, as God, He has the same nature as the Father and the Holy Ghost, He cannot be called Mediator, as God: for on 1 Tim. 2:5, "Mediator of God and man," a gloss says: "As the Word, He is not a Mediator, because He is equal to God, and God 'with God,' and at the same time one God." Therefore neither, as man, can He be called Mediator, on account of His having the same nature as men. ”