37 We have recently with sorrow censured the opinion of those who contend that marriage is the only means of assuring the natural development and perfection of the human personality. For there are those who maintain that the grace of the sacrament, conferred ex opere operato, renders the use of marriage so holy as to be a fitter instrument than virginity for uniting souls with God; for marriage is a sacrament, but not virginity. We denounce this doctrine as a dangerous error. Certainly, the sacrament grants the married couple the grace to accomplish holily the duties of their married state, and it strengthens the bonds of mutual affection that unite them; but the purpose of its institution was not to make the employment of marriage the means, most suitable in itself, for uniting the souls of the husband and wife with God by the bonds of charity.
Source: Sacra Virginitas (Vatican.va)