Objection 1. It would seem that husband and wife may take a vow contrary to the marriage debt without their mutual consent. For husband and wife are equally bound to pay the debt, as stated above (Article 5). Now it is lawful for the husband, even if his wife be unwilling, to take the cross in defense of the Holy Land: and consequently this is also lawful to the wife. Therefore, since this prevents the payment of the debt, either husband or wife may without the other's consent take the aforesaid vow.
Objection 2. Further, in taking a vow one should not await the consent of another who cannot dissent without sin. Now the husband or wife cannot, without sin, refuse their consent to the other's taking a vow of continence whether absolutely or for a time; because to prevent a person's spiritual progress is a sin against the Holy Ghost. Therefore the one can take a vow of continence either absolutely or for a time, without the other's consent.
Objection 3. Further, in the marriage act, the debt has to be demanded just as it has to be paid. Now the one can, without the other's consent, vow not to demand the debt, since in this he is within his own rights. Therefore he can equally take a vow not to pay the debt.
Objection 4. Further, no one can be bound by the command of a superior to do what he cannot lawfully vow or do simply, since one must not obey in what is unlawful. Now the superior authority might command the husband not to pay the debt to his wife for a time, by occupying him in some service. Therefore he might, of his own accord, do or vow that which would hinder him from paying the debt.
On the contrary, It is written (1 Corinthians 7:5): "Defraud not one another, except... by consent, for a time, that you may give yourselves to prayer."
Further, no one can vow that which belongs to another. Now "the husband... hath not power of his own body, but the wife" (1 Corinthians 7:4). Therefore, without her consent, the husband cannot take a vow of continence whether absolutely or for a time.
I answer that, A vow is a voluntary act, as its very name implies: and consequently a vow can only be about those goods which are subject to our will, and those in which one person is bound to another do not come under this head. Therefore in matters of this kind one person cannot take a vow without the consent of the one to whom he is bound. Consequently, since husband and wife are mutually bound as regards the payment of the debt which is an obstacle to continence, the one cannot vow continence without the other's consent; and if he take the vow he sins, and must not keep the vow, but must do penance for an ill-taken vow [Cf. 53, 1,4; 61, 1].
Reply to Objection 1. It is sufficiently probable that the wife ought to be willing to remain continent for a time, in order to succor the need of the universal Church. Hence in favor of the business for which the cross is given to him, it is laid down that the husband may take the cross without his wife's consent, even as he might go fighting without the consent of his landlord whose land he has leased. And yet the wife is not entirely deprived of her right, since she can follow him. Nor is there a parallel between wife and husband: because, since the husband has to rule the wife and not "vice versa," the wife is bound to follow her husband rather than the husband the wife. Moreover there would be more danger to the wife's chastity as a result of wandering from country to country, than to the husband's, and less profit to the Church. Wherefore the wife cannot take this vow without her husband's consent.
Reply to Objection 2. The one spouse, by refusing to consent to the other's vow of continence, does not sin, because the object of his dissent is to hinder not the other's good, but the harm to himself.
Reply to Objection 3. There are two opinions on this point. For some say that one can without the other's consent vow not to demand the debt, not however not to pay it, because in the former case they are both within their own rights, but not in the second. Seeing, however, that if one were never to ask for the debt, marriage would become too burdensome to the other who would always have to undergo the shame of asking for the debt, others assert with greater probability that neither vow can be lawfully taken by one spouse without the other's consent.
Reply to Objection 4. Just as the wife receives power over her husband's body, without prejudice to the husband's duty to his own body, so also is it without prejudice to his duty to his master. Hence just as a wife cannot ask her husband for the debt to the detriment of his bodily health, so neither can she do this so as to hinder him in his duty to his master. And yet the master cannot for this reason prevent her from paying the debt.
Source: Summa Theologica (New Advent)