I answer that, As stated above (Question [62], Articles [1],5), the sacraments of the New Law are ordained for a twofold purpose, namely, as a remedy for sin, and for the Divine worship. Now all the sacraments, from the fact that they confer grace, have this in common, that they afford a remedy against sin: whereas not all the sacraments are directly ordained to the Divine worship. Thus it is clear that penance, whereby man is delivered from sin, does not afford man any advance in the Divine worship, but restores him to his former state.
Now a sacrament may belong to the Divine worship in three ways: first in regard to the thing done; secondly, in regard to the agent; thirdly, in regard to the recipient. In regard to the thing done, the Eucharist belongs to the Divine worship, for the Divine worship consists principally therein, so far as it is the sacrifice of the Church. And by this same sacrament a character is not imprinted on man; because it does not ordain man to any further sacramental action or benefit received, since rather is it "the end and consummation of all the sacraments," as Dionysius says (Eccl. Hier. iii). But it contains within itself Christ, in Whom there is not the character, but the very plenitude of the Priesthood.
But it is the sacrament of order that pertains to the sacramental agents: for it is by this sacrament that men are deputed to confer sacraments on others: while the sacrament of Baptism pertains to the recipients, since it confers on man the power to receive the other sacraments of the Church; whence it is called the "door of the sacraments." In a way Confirmation also is ordained for the same purpose, as we shall explain in its proper place (Question [65], Article [3]). Consequently, these three sacraments imprint a character, namely, Baptism, Confirmation, and order.