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Rav Yehudah says that if the Yavam was sleeping during the Bi'ah, it is not a valid Yibum.
Rabah says if someone falls off the roof and in the process of falling he does Bi'ah with the Yevamah, it is not valid.
If a person is about to have relations with his own wife and he is physically forced to have relations with the Yevamah, it is a valid Yibum.
It is a Mitzvah l'Chatchilah for the Yavam to do Yibum rather than Chalitzah.
Only Bi'ah is a valid Yibum; it is not valid if it is done with money or a document.
Even if the Yibum is done against the will of the Yevamah, it is a valid Yibum.
If the Yevamah is sleeping during the Bi'ah, it is a valid Yibum.
A Yibum done while the Yavam was dozing is a valid Bi'ah. (1)
The liability of paying for embarrassing someone is incurred only if the perpetrator did so with intent.
If the Yavam attempts to ram against the wall and he instead rams into the Yevamah and does a Bi'ah, it is not a valid Yibum. (2)
Ula derives from a verse that a partial Bi'ah of a Nidah is regarded as a Bi'ah. (3)
A Yevamah is prohibited to the brothers if her husband is alive, even if he divorced her.
A partial Bi'ah of a male is regarded as a Bi'ah.
A partial Bi'ah of an animal is regarded as a Bi'ah.
The sister of a father is forbidden whether she is a sister from the father or from the mother.
A sister is forbidden whether she is a sister from the father or from the mother.
The wife of the brother of a father is forbidden by the Torah only if he is a brother from the father but not if he is only a brother from the mother.
The sister of a mother is forbidden whether she is a sister from the father or the mother.
The family of the father is regarded as family but not the family of the mother.
A BIT MORE
1. Although if the Yavam is sleeping during the Bi'ah it is not a valid Yibum, that is because he does not have the Bi'ah in mind, but if he is only dozing he does have the Bi'ah in mind and therefore it is valid.
2. This is because he did not have the Bi'ah in mind. If, however, the Yavam attempts to do Bi'ah with an animal and does Bi'ah with the Yevamah, it is a valid Yibum.
3. All of the other Arayos are derived from Nidah through a Hekesh.
A YIBUM THAT IS DONE WHILE SLEEPING
Rashi says that a Yibum done while sleeping is not valid because he is not a Bar Da'as and his Kinyan is not a valid Kinyan. The Tosfos Yeshanim asks that a Yibum that is done by a deaf mute is a valid Yibum even though he is not a Bar Da'as. The Rashba asks that a Shogeg and Mezid also should not be a valid Yibum according to Rashi, because they do not have a Kinyan in mind. Therefore, the Rashba explains that the reason why a Yibum is not valid while sleeping is because the Yavam must have in mind to do Bi'ah, and someone who is sleeping is not conscious of the Bi'ah.
PAYING FOR EMBARRASSMENT
A person is liable for embarrassing someone only if he embarrassed him with intent. One who embarrasses his friend unintentionally is exempt. Therefore, a sleeping person who causes embarrassment is exempt. Similarly, if a person berates his friend that he is a Moser, or that he stole, or that he caused him a loss in some other fashion, even though he cannot prove the charges he does not have to pay for embarrassment, since his intent was not to embarrass him. (Shulchan Aruch CM 421:1)
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