Commentaire sur Yevamot 9:2
וְאֵלּוּ מֻתָּרוֹת לִיְבָמֵיהֶן וַאֲסוּרוֹת לְבַעֲלֵיהֶן. כֹּהֵן גָּדוֹל שֶׁקִּדֵּשׁ אֶת הָאַלְמָנָה וְיֶשׁ לוֹ אָח כֹּהֵן הֶדְיוֹט, כָּשֵׁר שֶׁנָּשָׂא חֲלָלָה וְיֶשׁ לוֹ אָח חָלָל, יִשְׂרָאֵל שֶׁנָּשָׂא מַמְזֶרֶת וְיֶשׁ לוֹ אָח מַמְזֵר, מַמְזֵר שֶׁנָּשָׂא בַת יִשְׂרָאֵל וְיֶשׁ לוֹ אָח יִשְׂרָאֵל, מֻתָּרוֹת לִיְבָמֵיהֶן וַאֲסוּרוֹת לְבַעֲלֵיהֶן. אֲסוּרוֹת לָאֵלּוּ וְלָאֵלּוּ, כֹּהֵן גָּדוֹל שֶׁנָּשָׂא אֶת הָאַלְמָנָה וְיֶשׁ לוֹ אָח כֹּהֵן גָּדוֹל אוֹ כֹהֵן הֶדְיוֹט, כָּשֵׁר שֶׁנָּשָׂא חֲלָלָה וְיֶשׁ לוֹ אָח כָּשֵׁר, יִשְׂרָאֵל שֶׁנָּשָׂא מַמְזֶרֶת וְיֶשׁ לוֹ אָח יִשְׂרָאֵל, מַמְזֵר שֶׁנָּשָׂא בַת יִשְׂרָאֵל וְיֶשׁ לוֹ אָח מַמְזֵר, אֲסוּרוֹת לָאֵלּוּ וְלָאֵלּוּ. וּשְׁאָר כָּל הַנָּשִׁים, מֻתָּרוֹת לְבַעֲלֵיהֶן וְלִיְבָמֵיהֶן:
Et ceux-ci sont autorisés à leur yavmin et interdits à leurs maris: un grand prêtre qui a fiancé une veuve et qui a un frère qui est un Cohein régulier [Mais s'il l'épouse, elle devient une chalalah par sa cohabitation et est interdit aux deux le mari et le yavam.], un kasher qui a épousé une chalalah et qui a un frère qui est un chalal, un Israélite qui a épousé un mamzereth et qui a un frère qui est un mamzer, un mamzer qui a épousé la fille d'un Israélite, qui a un frère israélite. Ceux-ci sont autorisés à leur yavmin, mais interdits à leurs maris. Interdit aux deux: un grand prêtre qui a épousé une veuve, qui a un frère qui est soit un grand prêtre ou un prêtre ordinaire, un kasher qui a épousé une chalalah, qui a un frère qui est kasher, un israélite qui a épousé un mamzereth , qui a un frère qui est un Israélite, un mamzer qui a épousé la fille d'un Israélite, qui a un frère qui est un mamzer. Celles-ci sont interdites aux deux. Et toutes les autres femmes sont autorisées à leurs maris et à leurs yavmin.
Bartenura on Mishnah Yevamot
English Explanation of Mishnah Yevamot
A high priest who betrothed a widow and has a brother who is an ordinary priest;
A fit [priest] who married a halalah and has a brother who is a halal;
An Israelite who married a mamzeret and has a brother who is a mamzeret;
A mamzer who married the daughter of an Israelite and has a brother who is an Israelite. [In these cases the women] are permitted to their yevamim and forbidden to their husbands.
The following are forbidden to both;
A high priest who married a widow has a brother who is a high priest, or who is an ordinary priest;
A fir [priest] who married a halalah and has a brother who was a fit [priest];
An Israelite who married a mamzeret and has a brother who is Israelite;
A mamzer who married the daughter of an Israelite and has a brother who is a mamzer, [In these cases the women] are forbidden to both [the husband and the yavam]. All other women are permitted to both their husbands and their yevamim.
This mishnah continues to list types of women who are either forbidden to their husbands or to their yevamim.
Section one: A high priest is not allowed to marry a widow. If he betroths a widow and then dies, his brother, the ordinary priest, may have yibbum with her. However, if he married her, she would fall into the category of a halalah, that is a woman who has been disqualified from the priesthood. She would then be forbidden to the yavam brother as well.
Section two: A priest may not marry a halalah. However, if he has a brother who is a halal (for instance they have different mothers), then the brother may have yibbum with her.
Section three: An Israelite may not marry a mamzeret. However, if he has a brother who is a mamzer (they have different mothers), then the brother may have yibbum with her.
Section four: The opposite situation of that in section three.
Section five: The mishnah now begins to list women who are forbidden both to their husbands and, should the husbands die, to the yavam as well.
If a high priest marries a widow and dies and his brother is also a high priest, just as the first marriage was prohibited, so too is yibbum. Furthermore, since the first marriage was consummated (and did not remain only a betrothal, as in section one above), the woman became a halalah and is therefore prohibited to his brother even if he is only an ordinary priest.
Section six: If a fit priest marries a halalah, who is forbidden to him, she may not have yibbum with his brother who is also a fit priest.
Section seven: Just as the mamzereth was forbidden to the first husband, who was an ordinary Israelite, so too she is forbidden to his brother, if he is an ordinary Israelite.
Section eight: Just as the Israelite woman was forbidden to her first husband, who was a mamzer, so too she is forbidden to his mamzer brother.