2,739. Prohibiting One's Wife to Himself
Hilchos Nedarim 1:30
If a man tells his wife, “You are to me like my mother,” “like my sister,” “like orlah” or “like the mixed species of a vineyard,” It’s the same as if one says “May it be like pork” in reference to produce. Just as one may eat the produce in such a case as we previously discussed, he may likewise continue to be intimate with his wife. However, if he says, “I take a vow, prohibiting all benefit from you” or “The benefit of relations with you is prohibited to me,” then she is prohibited to him, as we shall see, IY”H.
Hilchos Nedarim 2:1
The rules of vows are the same regardless of whether one took a vow on his own or someone else spoke the vow for him and he answered amen, or something like amen in that he accepts the words.