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The seventh is the sacrament of matrimony, which is a sign of the union of Christ and the church according to the words of the apostle: This sacrament is a great one, but I speak in Christ and in the church. The efficient cause of matrimony is usually mutual consent expressed in words about the present. A threefold good is attributed to matrimony. The first is the procreation and bringing up of children for the worship of God. The second is the mutual faithfulness of the spouses towards each other. The third is the indissolubility of marriage, since it signifies the indivisible union of Christ and the church. Although separation of bed is lawful on account of fornication, it is not lawful to contract another marriage, since the bond of a legitimately contracted marriage is perpetual.
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It is asserted that some people reject fourth marriages as condemned. Lest sin is attributed where it does not exist, since the apostle says that a wife on her husband's death is free from his law and free in the Lord to marry whom she wishes, and since no distinction is made between the deaths of the first, second and third husbands, we declare that not only second and third marriages but also fourth and further ones may lawfully be contracted, provided there is no canonical impediment. We say, however, that they would be more commendable if thereafter they abstain from marriage and persevere in chastity because we consider that, just as virginity is to be preferred in praise and merit to widowhood, so chaste widowhood is preferable to marriage.
Source: https://www.ewtn.com/library/councils/florence.htm
Tag: goods of marriage