38 But considering the benefits of the Sacrament, besides the firmness and indissolubility, there are also much higher emoluments as the word "sacrament" itself very aptly indicates; for to Christians this is not a meaningless and empty name. Christ the Lord, the Institutor and "Perfecter" of the holy sacraments, by raising the matrimony of His faithful to the dignity of a true sacrament of the New Law, made it a sign and source of that peculiar internal grace by which "it perfects natural love, it confirms an indissoluble union, and sanctifies both man and wife."
Source: Casti Connubii (Vatican.va)