יורה דעה קנ״וYoreh De'ah 156

Se’if 1א׳

אֵין מִסְתַּפְּרִים מֵהָעוֹבֵד כּוֹכָבִים אֶלָּא בְּמָקוֹם שֶׁמְּצוּיִין בְּנֵי אָדָם, אוֹ אִם אוֹתוֹ הָעוֹבֵד כּוֹכָבִים מְדַמֶּה שֶׁאוֹתוֹ יִשְׂרָאֵל הוּא אָדָם חָשׁוּב. הַגָּה: וְיֵשׁ מַחְמִירִין שֶׁלֹּא לְהִסְתַּפֵּר מֵעוֹבֵד כּוֹכָבִים, אֲפִלּוּ בִּמְקוֹם רַבִּים, בְּתַעַר, אִם לֹא שֶׁיִּרְאֶה בְּמַרְאָה. (תּוֹסָפוֹת וּמָרְדְּכַי פא"מ). וְנָהֲגוּ לְהָקֵל כִּסְבָרָא רִאשׁוֹנָה.

They do not have their hair cut by an idolater (oved kokhavim — the standing term for a gentile) except in a place where men are to be found, or if that idolater supposes that that Israelite is an important man. Hagah [Rema]: And there are those who are stringent not to have one's hair cut by an idolater with a razor, even in a place of many, unless he looks in a mirror. (Tosafot and Mordechai, chapter "They do not leave") And they have been accustomed to be lenient in accordance with the first reasoning.

Se’if 2ב׳

אָסוּר לְאִישׁ לְהִסְתַּכֵּל בְּמַרְאָה, מִשּׁוּם לֹא יִלְבַּשׁ גֶּבֶר (דְּבָרִים כב, ה), אֶלָּא אִם כֵּן מִשּׁוּם רְפוּאָה, כְּגוֹן שֶׁחוֹשֵׁשׁ בְּעֵינָיו, אוֹ שֶׁמְּסַפֵּר עַצְמוֹ, אוֹ אִם מִסְתַּפֵּר מִן הָעוֹבֵד כּוֹכָבִים בֵּינוֹ לְבֵינוֹ. וּכְדֵי לֵרָאוֹת אָדָם חָשׁוּב, מֻתָּר לִרְאוֹת בְּמַרְאָה. הַגָּה: וְיֵשׁ אוֹמְרִים הָא דְּאָסוּר לִרְאוֹת בְּמַרְאָה הַיְנוּ דַּוְקָא בְּמָקוֹם דְּאֵין דֶּרֶךְ לִרְאוֹת בְּמַרְאָה רַק נָשִׁים, וְאִית בֵּיהּ מִשּׁוּם לֹא יִלְבַּשׁ גֶּבֶר (דְּבָרִים כב, ה) אֲבָל בְּמָקוֹם שֶׁדֶּרֶךְ הָאֲנָשִׁים לִרְאוֹת גַּם כֵּן בְּמַרְאָה, מֻתָּר. (ר"ן פא"מ). וַאֲפִלּוּ בְּמָקוֹם שֶׁנָּהֲגוּ לְהַחְמִיר, אִם עוֹשֶׂה לִרְפוּאָה שֶׁמֵּאִיר עֵינָיו, אוֹ שֶׁעוֹשֶׂה לְהָסִיר הַכְּתָמִים מִפָּנָיו אוֹ נוֹצוֹת מֵרֹאשׁוֹ, שָׁרֵי. (סְמַ"ג בְּשֵׁם הר"ר זֶעְלְקִיל). וְכֵן נָהֲגוּ. וְעַיֵּן לְקַמָּן סִימָן קפ"ב.

It is forbidden for a man to look in a mirror, on account of "a man shall not put on a woman's garment" (Deuteronomy 22:5) — unless it is for the sake of healing, such as where he suffers in his eyes, or where he cuts his own hair, or if he has his hair cut by an idolater when the two of them are alone. And in order to be seen as an important man, it is permitted to look in a mirror. Hagah [Rema]: And there are those who say that this, that it is forbidden to look in a mirror, is specifically in a place where it is not the way to look in a mirror save for women, and there is in it the matter of "a man shall not put on a woman's garment" (Deuteronomy 22:5); but in a place where it is the way of men also to look in a mirror, it is permitted. (the Ran, chapter "They do not leave") And even in a place where they have been accustomed to be stringent, if he does it for healing, that it brightens his eyes, or if he does it to remove the blemishes from his face or feathers from his head, it is permitted. (Semag in the name of Rabbi Zelkil) And so they have been accustomed. And see below, siman 182.

Se’if 3ג׳

יִשְׂרָאֵל הַמְסַפֵּר אֶת הָעוֹבֵד כּוֹכָבִים, כֵּיוָן שֶׁהִגִּיעַ סָמוּךְ לִבְלוֹרִיתוֹ ג' אֶצְבָּעוֹת מִכָּל רוּחַ, שׁוֹמֵט יָדוֹ. וְכֵן הַקָּרְחָה שֶׁעוֹשִׂים הַכֹּהֲנִים, אָסוּר (לְיִשְׂרָאֵל) לַעֲשׂוֹת לָהֶם.

An Israelite who cuts the hair of an idolater: once he has come within three fingerbreadths on every side of his blorit (the forelock grown for idolatry), he withdraws his hand. And likewise the bald patch that the priests make, it is forbidden (for an Israelite) to make for them.