Gemara

Question: When an Arus annuls alone, does he cut half the vow (but the remainder is a full-strength vow)? Or, does he weaken the vow?

This pertains to one who vowed from two olives, and her husband annulled the vow, and she ate the olives. If he cuts the vow (and does not weaken it), she is lashed;

If he weakens it, she is not lashed.

Answer (Beraisa) Question: When do we say that that if the Arus dies, the father gets back authority to annul?

Answer: It is when the Arus died without hearing the vow, or after he annulled it, or if he died on the day he heard it, before he acted on it;

If the Arus affirmed the vow, or was silent on the day he heard it and died on a later day, the father cannot annul it.

If the father heard her vow and annulled it and died before the Arus heard it, authority to annul does not pass to the Arus.

If the Arus heard her vow and annulled it and died before the father heard it, authority to annul returns to the father.

If the Arus heard her vow and annulled it and the father died before hearing it, the Arus cannot annul it, since he can annul only in partnership.

If the father heard her vow and annulled it and the Arus died before he heard it, the father can annul the portion of her vow that remained to the Arus;

R. Noson says, this is Beis Shamai's opinion. Beis Hillel say that he cannot annul.

Inference (and summation of answer): Beis Shamai hold that the father cuts the vow. (The same applies to the Arus.) Beis Hillel hold that he weakens it.

72a (Mishnah): If an Arusah vowed, was divorced that same day, and became Mekudeshes again the same day, even 100 times that day, her father and the last Arus annul her vows.

The case is, the first Arus did not hear the vow.

Question: If so, why does the Mishnah say that she remarried the same day? The same law would apply even if she remarried 100 days later!

Answer: The case is, the Arus did not hear, but the father heard. Since the father can annul only that day, she must remarry that day to enable joint annulment.

Rishonim

The Rif brings the Gemara verbatim.

Rambam (Hilchos Nedarim 12:17): If a Na'arah Me'orasah vowed and her father heard and annulled it, and days later her Arus heard and annulled it, it is not annulled. "V'Im Heni Aviha Osah b'Yom Shom'o" and "v'Shoma Ishah b'Yom Shom'o" teach that Hafarah must be on the day that her father and Arus heard. Likewise, if her Arus heard and annulled it, and days later her father heard and annulled it, it is not annulled.

Taz (YD 234:6): The words "v'Shoma Ishah b'Yom Shom'o" (Bamidbar 30:8) are totally unnecessary. Obviously, he hears on the day he hears! The Rambam deduced that b'Yom Shom'o refers back to verse 5, "v'Shoma Aviha"; the Arus must hear on the same day that her father heard. Those who disagree hold that b'Yom Shom'o refers to the next words "v'Hecherish Lah", and teaches that silence depends on the entire day.

Note: The Rambam does not need it to teach about silence the entire day, for the next verse teaches that Hafaras Arus must be on the day that he hears (Lechem Mishneh).

Gra (YD 234:13): The Rambam learned from the Sifri, which learns from sources other than b'Yom Shom'o that Hafarah must be on the day the Arus heard.

Radvaz: SMaG derives this law from the Gemara (72a). His text said 'the Arus can annul only that day'. However, our text says 'the father can annul only that day.' I.e., when the Arus did not annul and the father inherited his authority, it must be the same day (but when each annuls, it suffices for each to annul on the day that he heard).

Question (Lechem Mishneh): Even according to the text of the SMaG, what is the proof? The Beraisa discusses when she became Mekudeshes again on the same day, for if not, we would not need the new Arus! If the father annulled on the day he heard, this works by itself, for he got all the authority of the first Arus! If the father did not annul on the day he heard, this is Kiyum!

Rosh (10:2): If the Arus died without hearing it, or heard it and annulled it or was silent, his authority passes to the father. The father can annul on the day he hears. This need not be the day that the Arus heard. Since the husband died on the day he heard, the father inherits his authority. It was not affirmed by the husband. However, if the husband heard and affirmed or was silent the entire day and died the next day, the father cannot annul.

Beis Yosef (YD 234 DH veha'Ramban): The Rosh holds like the Ramban, that the husband and Arus can annul on different days.

Rebuttal (Lechem Mishneh and Gra 14): There is no source to say so! The Rosh discusses only when the father inherits the Arus' authority and annuls by himself! This is why the Tur did not cite the Ramban's opinion in the name of the Rosh.

Ran (68a DH Ta): The Beraisa discussed the Arus dying on the day he heard the vow only when he did not annul it. Had he lived the entire day without annulling, this would be Kiyum. When he annulled it, even if he dies later the father can annul on the day the father hears. Even though the Arus' Hafarah is Batel and the father must annul also the Arus' share, we cannot consider it as if the Arus affirmed, for he showed that he wants to annul. The Seifa teaches that if the Arus affirmed the vow, or was silent on the day he heard it and died on a later day, the father cannot annul it. It did not teach that the father cannot annul if the Arus annulled and died on a later day!

Poskim

Shulchan Aruch (YD 234:5): If the Arus or father annulled by himself, it is not annulled. However, the other's part is weaker, and the Isur is lighter. There are no lashes. Both of them must hear on the same day. If one heard today and annulled, and the other heard another day, he cannot annul. Some say that each annuls on the day that he hears, even if the other heard on a different day.

Taz (6): The Tur favors the latter opinion. The Shulchan Aruch is stringent, for it is a Safek mid'Oraisa.