(Mishnah): The Klal (general rule) is, any Isur of Ervah does neither Yibum nor Chalitzah;

An Isur of Mitzvah (Arayos mid'Rabanan, like the coming Mishnah explains) or Isur Kedushah (Chayavei Lavim) does Chalitzah but not Yibum.

Her sister that is his Yevamah does Chalitzah or Yibum.

(Gemara - R. Ze'ira): When I was there (in Bavel), I found for 14 (of the 15 Arayos in Mishnah 1:1) 'her sister is her Yevamah, she can do Yibum', [i.e. all 15] except for his daughter;

When I came to here (Eretz Yisrael), I heard what R. Chiyah taught;

(R. Chiyah - Beraisa): [Reuven]'s daughter through rape, who married his paternal brother (Shimon), and she has a maternal sister from another man, married to a second brother (Levi), and [Shimon and Levi] died, [Reuven] is forbidden to his daughter and permitted to her sister.

This is the case in which 'her sister is her Yevamah, she can do Yibum.'

The following is obvious. An Isur of Mitzvah or Isur Kedushah, (since mid'Oraisa he may do Yibum,) if he did Chalitzah to her, her Tzarah is exempted.

Implied question: If he had Bi'ah with her [what is the law]?

Answer #1 (R. Yosah): [Amora'im] argue about this. R. Lazar says that her Tzarah is not exempted, and R. Yochanan says that she is exempted.

Answer #2 (R. Shamai): They said oppositely. (R. Lazar says that she is exempted, and R. Yochanan disagrees.)

Support: Presumably, R. Shamai is correct, for everywhere R. Lazar is close to R. Chiyah Rabah, and R. Chiyah taught that Isur of Mitzvah or Isur Kedushah, he did Chalitzah to or had Bi'ah with her, her Tzarah is exempted.

(Mishnah): Isurim of Mitzvah are Sheniyos (Isurim) mid'Rabanan.

Isurim of Kedushah are a widow to a Kohen Gadol, a divorcee or a Chalutzah to a regular Kohen, a Mamzeres or Nesinah to a Yisrael, and a Bas Yisrael to a Nasin or Mamzer.

(Gemara): Isurim of Mitzvah are Arayos mid'Rabanan. [They are called Isurei Mitzvah, for] it is a Mitzvah from the Torah to obey Chachamim.

Isurim of Kedushah are a widow to a Kohen Gadol, a divorcee or a Chalutzah to a regular Kohen. [They are called Isurei Kedushah, based on] "v'Kidashto Ki Lechem Elokecha Hu Makriv."

Some switch them. Isurei Mitzvah are a widow to a Kohen Gadol, a divorcee or a Chalutzah to a regular Kohen, for it says "Elu ha'Mitzvos" They are called Isurei Kedushah, based on] "v'Kidashto Ki Lechem Elokecha Hu Makriv."

Isurei Kedushah are Arayos mid'Rabanan;

(R. Yudah bar Pazi): Why did the Torah put Parshas Arayos next to Parshas Kedoshim? This teaches that anyone who separates from Arayos is called Kadosh;

So the Shunamis told her husband "I know that Ish ha'Elokim (Elisha) is Kadosh";

(R. Yonah): He is Kadosh, but his Talmid (Gechazi) is not Kadosh.

(R. Avin): [She said that Elisha is Kadosh] because he did not look at her.

(Rabanan): It is because he never saw a drop of semen all his days.

Note: She said so before they built a room for him to sleep there! Perhaps Rabanan agree that she said so because he did not look at her, but they hold that it is recorded in the Navi because he never saw Keri.

The servant of R. Shmuel bar Rav Yitzchak said 'all my days, I never saw a lowly matter (semen) on my master's garments.'

Question: It says "va'Yigash Gechazi Lehadfah" - what is Lehadfah?

Answer (R. Yosi ben Chaninah): He put his hand in the Hod (peak) of her beauty [to push her away], i.e. between her breasts.