יבמות י״בYevamot 12

Mishnah 1א׳

מִצְוַת חֲלִיצָה בִּשְׁלֹשָׁה דַיָּנִין, וַאֲפִלּוּ שְׁלָשְׁתָּן הֶדְיוֹטוֹת. חָלְצָה בְמִנְעָל, חֲלִיצָתָהּ כְּשֵׁרָה. בְּאַנְפִּילִין, חֲלִיצָתָהּ פְּסוּלָה. בְּסַנְדָּל שֶׁיֶּשׁ לוֹ עָקֵב, כָּשֵׁר. וְשֶׁאֵין לוֹ עָקֵב, פָּסוּל. מִן הָאַרְכֻּבָּה וּלְמַטָּה, חֲלִיצָתָהּ כְּשֵׁרָה. מִן הָאַרְכֻּבָּה וּלְמַעְלָה, חֲלִיצָתָהּ פְּסוּלָה:

The Mitzvah of Chalitzah [the ceremony releasing the widow of a childless man from the obligation of Levirate marriage, takes place before a court of] three judges, even if the three are laymen. If she performs Chalitzah with a shoe her Chalitzah is valid, but [if she used] a cloth slipper her Chalitzah is invalid. [If it was done] with a sandal which has a heel it is valid, but with no heel - it is not valid. [If she untied the shoe's straps] from the knee and below - her Chalitzah is valid, [but] if from the knee and above - her Chalitzah is invalid.

Mishnah 2ב׳

חָלְצָה בְסַנְדָּל שֶׁאֵינוֹ שֶׁלּוֹ, אוֹ בְסַנְדָּל שֶׁל עֵץ, אוֹ בְשֶׁל שְׂמֹאל בַּיָּמִין, חֲלִיצָתָהּ כְּשֵׁרָה. חָלְצָה בְגָדוֹל שֶׁהוּא יָכוֹל לַהֲלוֹךְ בּוֹ, אוֹ בְקָטָן שֶׁהוּא חוֹפֶה אֶת רֹב רַגְלוֹ, חֲלִיצָתָהּ כְּשֵׁרָה. חָלְצָה בַלַּיְלָה, חֲלִיצָתָהּ כְּשֵׁרָה, וְרַבִּי אֱלִיעֶזֶר פּוֹסֵל. בַּשְּׂמֹאל, חֲלִיצָתָהּ פְּסוּלָה, וְרַבִּי אֱלִיעֶזֶר מַכְשִׁיר:

[If] she performed Chalitzah with a sandal which is not his [the Yavam - one upon whom has fallen the obligation to perform Levirate marriage], or with a sandal of wood, or with the left [sandal worn] on the right foot - her Chalitzah is valid. [If] she performed Chalitzah with [a sandal] which was too large [for him] but with which he was able to walk [anyway], or with one too small [for him], but which [nevertheless] covers most of his foot, her Chalitzah is valid. [If] she performed Chalitzah at night her Chalitzah is valid, but Rabbi Eliezer deems it invalid. [If] she performed Chalitzah on his left [foot] her Chalitzah is invalid, but R. Eliezer deems it valid.