41 In the great confusion of opinions, however, which day by day is spreading more and more widely, it should further be known that no power can dissolve the bond of Christian marriage whenever this has been ratified and consummated; and that, of a consequence, those husbands and wives are guilty of a manifest crime who plan, for whatever reason, to be united in a second marriage before the first one has been ended by death. When, indeed, matters have come to such a pitch that it seems impossible for them to live together any longer, then the Church allows them to live apart, and strives at the same time to soften the evils of this separation by such remedies and helps as are suited to their condition; yet she never ceases to endeavor to bring about a reconciliation, and never despairs of doing so. But these are extreme cases; and they would seldom exist if men and women entered into the married state with proper dispositions, not influenced by passion, but entertaining right ideas of the duties of marriage and of its noble purpose; neither would they anticipate their marriage by a series of sins drawing down upon them the wrath of God.
Source: Arcanum Divinae (Vatican.va)