Objection 1. It would seem that a sacred order cannot supervene to matrimony. For the stronger prejudices the weaker. Now a spiritual obligation is stronger than a bodily tie. Therefore if a married man be ordained, this will prejudice the wife, so that she will be unable to demand the debt, since order is a spiritual, and marriage a bodily bond. Hence it would seem that a man cannot receive a sacred order after consummating marriage.
Objection 2. Further, after consummating the marriage, one of the parties cannot vow continence without the other's consent [Cf. 61, 1]. Now a sacred order has a vow of continence annexed to it. Therefore if the husband be ordained without his wife's consent, she will be bound to remain continent against her will, since she cannot marry another man during her husband's lifetime.
Objection 3. Further, a husband may not even for a time devote himself to prayer without his wife's consent (1 Corinthians 7:5). But in the Eastern Church those who are in sacred orders are bound to continence for the time when they exercise their office. Therefore neither may they be ordained without their wife's consent, and much less may the Latins.
Objection 4. Further, husband and wife are on a par with one another. Now a Greek priest cannot marry again after his wife's death. Therefore neither can his wife after her husband's death. But she cannot be deprived by her husband's act of the right to marry after his death. Therefore her husband cannot receive orders after marriage.
Objection 5. Further, order is as much opposed to marriage as marriage to order. Now a previous order is an impediment to a subsequent marriage. Therefore, etc.
On the contrary, Religious are bound to continence like those who are in sacred orders. But a man may enter religion after marriage, if his wife die, or if she consent. Therefore he can also receive orders.
Further, a man may become a man's bondsman after marriage. Therefore he can become a bondsman of God by receiving orders.
I answer that, Marriage is not an impediment to the receiving of sacred orders, since if a married man receive sacred orders, even though his wife be unwilling, he receives the character of order: but he lacks the exercise of his order. If, however, his wife consent, or if she be dead, he receives both the order and the exercise.
Reply to Objection 1. The bond of orders dissolves the bond of marriage as regards the payment of the debt, in respect of which it is incompatible with marriage, on the part of the person ordained, since he cannot demand the debt, nor is the wife bound to pay it. But it does not dissolve the bond in respect of the other party, since the husband is bound to pay the debt to the wife if he cannot persuade her to observe continence.
Reply to Objection 2. If the husband receive sacred orders with the knowledge and consent of his wife, she is bound to vow perpetual continence, but she is not bound to enter religion, if she has no fear of her chastity being endangered through her husband having taken a solemn vow: it would have been different, however, if he had taken a simple vow. On the other hand, if he be ordained without her consent, she is not bound in this way, because the result is not prejudicial to her in any way.
Reply to Objection 3. It would seem more probable, although some say the contrary, that even a Greek ought not to receive sacred orders without his wife's consent, since at least at the time of his ministry she would be deprived of the payment of the debt, of which she cannot be deprived according to law if the husband should have been ordained without her consent or knowledge.
Reply to Objection 4. As stated, among the Greeks the wife, by the very fact of consenting to her husband's receiving a sacred order, binds herself never to marry another man, because the signification of marriage would not be safeguarded, and this is especially required in the marriage of a priest. If, however, he be ordained without her consent, seemingly she would not be under that obligation.
Reply to Objection 5. Marriage has for its cause our consent: not so order, which has a sacramental cause appointed by God. Hence matrimony may be impeded by a previous order; so as not to be true marriage: whereas order cannot be impeded by marriage, so as not to be true order, because the power of the sacraments is unchangeable, whereas human acts can be impeded.
Source: Summa Theologica (New Advent)