Pope Gregory XVI (2 February 1831 – 1 June 1846) served in a chaotic period of European history. The French Revolution had uprooted the traditional way of life from most Europeans. Gregory was concerned that too much of the Christian tradition was being set aside. In one paragraph of his encyclical Mirari Vos, he defends the sacramental and indissolubility of marriage.
Now the honorable marriage of Christians, which Paul calls “a great sacrament in Christ and the Church,” demands our shared concern lest anything contrary to its sanctity and indissolubility is proposed. Our predecessor Pius VIII would recommend to you his own letters on the subject. However, troublesome efforts against this sacrament still continue to be made. The people therefore must be zealously taught that a marriage rightly entered upon cannot be dissolved; for those joined in matrimony God has ordained a perpetual companionship for life and a knot of necessity which cannot be loosed except by death. Recalling that matrimony is a sacrament and therefore subject to the Church, let them consider and observe the laws of the Church concerning it. Let them take care lest for any reason they permit that which is an obstruction to the teachings of the canons and the decrees of the councils. They should be aware that those marriages will have an unhappy end which are entered upon contrary to the discipline of the Church or without God’s favor or because of concupiscence alone, with no thought of the sacrament and of the mysteries signified by it.
—Pope Gregory XVI, Mirari Vos #12, August 15, 1832 (Italics original, bold added)