Thomas Aquinas

“ As regards other advantages resulting from matrimony, such as the friendship and mutual services which husband and wife render one another, its institution belongs to the civil law. Since, however, a sacrament is essentially a sign and a remedy, it follows that the nature of sacrament applies to matrimony as regards the intermediate institution; that it is fittingly intended to fulfill an office of nature as regards the first institution ”

“ And so they say that it makes man withdraw from evil, by restraining the concupiscence lest it tend to something outside the marriage blessings, but that this grace does not enable a man to do good works. But this cannot be maintained, since the same grace hinders sin and inclines to good, just as the same heat expels cold and gives heat.
Hence others [*St. Bonaventure, Sent. iv, D, 26] say that matrimony, inasmuch as it is contracted in the faith of Christ, is able to confer the grace which enables us to do those works which are required in matrimony. ”

“ Before sin matrimony was instituted by God, when He fashioned a helpmate for man out of his rib, and said to them: "Increase and multiply." And although this was said also to the other animals, it was not to be fulfilled by them in the same way as by men. As to Adam's words, he uttered them inspired by God to understand that the institution of marriage was from God.
Reply to Objection 5: As was clearly stated, matrimony was not instituted before Christ as a sacrament of the New Law.
Art. 3 - Whether matrimony confers grace? Objection 1: It would seem that matrimony does not confer grace. ”

“ Things which are of natural law in a general way, need to be instituted as regards their determination which is subject to variation according to various states; just as it is of natural law that evil-doers be punished, but that such and such a punishment be appointed for such and such a crime is determined by positive law. ”

“ Therefore, since in matrimony man receives by Divine institution the faculty to use his wife for the begetting of children, he also receives the grace without which he cannot becomingly do so; just as we have said of the sacrament of orders ( [4927] Q [35] , A [1] ) . And thus this grace which is given is the last thing contained in this sacrament. ”