I see you discovered the obscure passages of Numbers 30.
Vows Taken by A Young Woman in Her Father's House
Numbers 30:3-5
Vows Taken by a Married Woman
Numbers 30:6-8
Vows Taken by a Widow or Divorced Woman
Numbers 30:9-12
Context: Vows to "Afflict Herself"
Numbers 30:13-15
All right: so what does all of this mean? The key is in the final section;
the chapter is concerned with a woman's vows to "afflict herself," which, as the great Torah scholar Jacob Milgrom points out, was interpreted by ancient Jews as referring to fasting and refraining from sexual intercourse. Similar terminology is used in descriptions of the Day of Atonement, when Jews were expected to fast and refrain from sexual intercourse (see Milgrom, Harper Collins Study Bible n. Lev 16:29; citing Targum Pseudo-Jonthan; cf. also Exod 19:15).(one day a year, no big deal)
Once this terminology is clear, the whole chapter makes sense. It is discussion three kinds of vows:
1. Vows of sexual abstinence taken by a young, unmarried woman.
2. Vows of sexual abstinence taken by a married woman.
3. Vows of sexual abstinence taken by a widow or divorced woman.
In all three cases,
the binding nature of the vow is dependant on whether the male party (whether father or husband), upon hearing of the vow,
said nothing and in thereby consented to it. In each case,
if he heard the vow and accepted it, the vow is perpetually binding.
Now, what this means is that if a young Jewish woman--say, Mary, in this instance--took a vow of sexual abstinence, and her legal husband--in our case, Joseph--heard of the vow
and said nothing, then the vow stands, and
she is bound to keep it. This provides
a solid historical basis for Joseph and Mary having a perpetually virginal marriage: indeed, Numbers is very explicit in the final verse that if the husband changes his mind "and makes them null and void after he has heard of them," the
the sin will be upon him: "
he shall bear her iniquity" (Num 30:15). One can easily imagine a situation where some husbands would think better of deciding to accept such a vow! But as Matthew's Gospel tells us:
Joseph was a "righteous man" (Matthew 1:19), and obedient to Torah.
If Mary took a vow of sexual abstinence--and her words
"How can this be, since I know not man?" in Luke are evidence that she did (Luke 1:34)--
and if Joseph accepted this vow at the time of their wedding, then he would have been bound by Mosaic Law to honor her vow of sexual abstinence under the penalty of sin.
(if Joseph were to violate Mosaic Law and disobey the Torah, then Scripture wouldn't call him "righteous")
However implausible it may sound to a sex-saturated Western culture that a man would ever do such a thing, the fact of the matter is that the Old Testament appears to assume it as a real possibility. Indeed, the fact that an
entire chapter of the Bible is devoted to it appears to suggest that vows of sexual abstinence on the part of women must have been a visible enough part of the culture that a law was necessary to deal with the situation! (This should come as no surprise to students of antiquity;
consecrated virgins were part of the religious landscape of the ancient world).
Should there be any doubt about this, I would suggest in passing that the reader call to mind the controversy that faced Pauline churches about young widows renegging on their vows of sexual abstinence (1 Timothy 4) and the otherwise difficult and confusing passage in 1 Corinthians about what a man should do about marrying his "virgin" (1 Cor 7:36-38). If both these texts apply to the situation envisaged in Numbers 30,
then Mary's situation is anything but unique in culture.
http://www.thesacredpage.com/2008/03/biblical-basis-for-marys-perpetual.html