6 Wherefore this in the first place you ought to know, that by the good, which you have chosen, second marriages are not condemned, but are set in lower honor. For, even as the good of holy virginity, which your daughter has chosen, does not condemn your one marriage; so neither does your widowhood the second marriage of any. For hence, specially, the heresies of the Cataphryges and of the Novatians swelled, which Tertullian also, inflated with cheeks full of sound not of wisdom, while with railing tooth he attacks second marriages, as though unlawful, which the Apostle with sober mind allows to be altogether lawful.
From this soundness of doctrine let no man's reasoning, be he unlearned, or be he learned, move you; nor should you so extol your own good, as to charge as evil that of another's which is not evil; but you should rejoice so much the more of your own good, the more you see, that, by it, not only are evils shunned, but some goods too surpassed. For adultery and fornication are evils. But from these unlawful things she is very far removed, who has bound herself by liberty of vow, and, not by command of law, but by counsel of charity, has brought to pass that even things lawful should not be lawful to her.
And marriage chastity is a good, but widowed continence is a better good. Therefore this better good is honored by the submission of that other, not that other condemned by the praise of this that is better.
Source: On the Good of Widowhood (New Advent)