Marriage and Virginity
for the one with the faith either to be forbidden by God to divorce the unbeliever or to be commanded to do so. It was not proper for it to be forbidden, as justice allows separation from someone who commits adultery, and the adultery in the heart of an unbeliever is the worst.
Also, the unbeliever's chastity in relation to the marriage partner cannot be called true chastity, since everything that does not come from faith is sinful (Rom 14:23). On the other hand, the partner who believes has true chastity, even in relation to the unbelieving partner who does not have true chastity. The reason why it was also not proper for the faithful to be commanded to separate from unbelievers is that when they married they were both Gentiles and they were not doing anything that God forbade.
21. Because the Lord neither commands the believer to leave the unbeliever, nor forbids it, this is why it is not the Lord but the apostle who says not to leave. Certainly he possesses the Holy Spirit, which enables him to give advice that is useful and reliable. This is why, when he said to the woman whose husband had died, In my opinion she will be happier if she stays as she is (1 Cor 7:40), he added, I believe, though, that I too have the Spirit of God, so that no one would think that his advice should be dismissed as merely human and not from God.
Hence we must appreciate that when something the Lord does not command is recommended as beneficial by his holy servant, this recommendation is also inspired by God. When the Holy Spirit gives advice, far be it from the thoughts of any Catholic to say that it is not the Lord who gives the advice. The Spirit is Lord too, and the works of the Trinity are indivisible.
Nevertheless he says, About virgins I have no commandment from the Lord, but I give advice (1 Cor 7:24). This is not to have us think that this advice is different from what the Lord would give, since he immediately goes on to say, as someone who by God's mercy is faithful to him. The advice he gives, therefore, is true to what God wants and comes from that Spirit of whom he says, I believe, though, that I too have God's Spirit (1 Cor 7:40).
22. Just the same, a command given by God in the exercise of his authority is one thing, but the faithful advice of a fellow slave based on the compassionate love that he has by the inspiration and gift of the Lord is something else. In the first case it is wrong to act otherwise; in the other case it is not wrong, but in such a way that sometimes indeed it is good to do the thing that is not wrong but sometimes it is not good. It is good to do it on those occasions when not only is it permitted in justice, which God upholds, but also it does nothing to hinder the salvation of others. It is like this when the apostle gives virgins the advice not to marry,