Ketubot, Chapter Five, Mishnah Three
This mishnah is a continuation of yesterdays mishnah. It continues to discuss when a woman may begin to eat terumah.
1) A yavam [who is a priest] does not allow [his sister-in-law] to eat terumah.
2) If she had spent six months waiting for her husband and six months waiting for the yavam, or even [if she spent] all of them waiting for her husband less one day waiting for the yavam, or all of them waiting for the yavam less one day waiting for her husband, she may not eat terumah.
3) This [was the ruling according to] the first mishnah.
a) The court that followed afterwards ruled: a woman may not eat terumah until she has entered the bridal chamber.
Section one: If a woman is widowed while merely betrothed to her husband, her yavam does not allow her to eat terumah until he has had yibbum with her (see also Mishnah Yevamot 7:4).
Section two: Yesterday we learned that a betrothed woman is given one year to prepare herself from the time a husband requests her in marriage. If he delays any longer, she may claim maintenance from his estate, and she may eat terumah. Our mishnah teaches that if she waited part of this time for the husband and part for the yavam, she does not eat terumah, even though a full year has passed. She may only eat terumah if she waits a full year either for the yavam or for the husband. However, if she does wait a full year for the yavam and he does not marry her (or perform halitzah) she begins to eat from his estate and she may begin to eat terumah (provided, of course, that he is a priest).
Section three: According to yesterdays mishnah a woman might begin to eat terumah before she enters the huppah (the bridal chamber). This would occur, if she waits for a full year and her husband does not marry her. Our mishnah says that this was an earlier position, but that later tannaim ruled that in no case may a woman eat terumah before she is fully married, an act which occurs when she enters the huppah. In the Talmud there is a debate as to why the later court disallowed a woman to eat terumah until she entered the huppah. The first opinion is that if she eats while still in her fathers home she may give some terumah to her family members who are not priests. Once she moves to her husbands home we are not concerned with such a possibility. The second opinion is that before she enters the huppah, her husband can annul the marriage (we need not get into here how this is performed). If he were to do so, retroactively she would have been a non-priest who ate terumah. However, once the marriage is finalized, he can no longer annul the marriage and there is no such concern.