That a high priest not enter the tent of a dead body: That a high priest not enter the tent of a dead body — and even for one of the six commanded dead [relatives], as it is stated (Leviticus 21:11), “And for all dead souls, he shall not come” — meaning to say, he should not enter into the house with them. As the expression, “he shall not come” implies entering [entering a house].
What I wrote above in Mitzvah 266 in this Order (Sefer HaChinukh 263) is from the roots of the commandment — that it is fitting to distance the priests, who are the holy ones who do the service of God, from the matter of impurity. And [regarding] the high priest who is distinguished to be Holy of Holies; though he has a body, his soul always dwells among the elevated servants. Therefore, the Torah is not concerned to ever permit him impurity — even for the relatives which the Torah is concerned about for the ordinary priests, which I wrote about above (Sefer HaChinukh 263), who will pour out their souls in the house of [mourning] because their hearts are heated for their relatives. The high priest, by contrast, is thoroughly bound to loftier pursuits and entirely separate from human nature. He will lose any memory of this fleeting world; he will not weep for the loss of one of his society because he was already apart from them in life. As far as the laws of impurity from the dead and the tent of the dead, I have already spoken some according to my custom in this Order; it is not fitting to repeat it, lest it become burdensome for the reader. (See Mishneh Torah, Laws of Mourning 3.)
And this prohibition is practiced at the time of the [Temple] when there was a High Priest there. And in any place that he may be — even if on some occasion he exited the Land — he is [still forbidden] from entering into the tent of a dead body. And if he transgressed and entered there volitionally — even [if it was] his father or mother [that] were dead in the house — he is lashed.
שֶׁלֹּא יִכָּנֵס כֹּהֵן גָּדוֹל בְּאֹהֶל הַמֵּת – שֶׁלֹּא יִכָּנֵס כֹּהֵן גָּדוֹל בְּאֹהֶל הַמֵּת וַאֲפִלּוּ לְשִׁשָּׁה מֵתֵי מִצְוָה, שֶׁנֶּאֱמַר (ויקרא כא יא) וְעַל כָּל נַפְשֹׁת מֵת לֹא יָבֹא. כְּלוֹמַר לֹא יָבוֹא בְּתוֹךְ הַבַּיִת עִמָּהֶם, דִּלְשׁוֹן לֹא יָבוֹא בִּיאַת בַּיִת מַשְׁמַע.
That a high priest not enter the tent of a dead body: That a high priest not enter the tent of a dead body — and even for one of the six commanded dead [relatives], as it is stated (Leviticus 21:11), “And for all dead souls, he shall not come” — meaning to say, he should not enter into the house with them. As the expression, “he shall not come” implies entering [entering a house].
מִשָּׁרְשֵׁי הַמִּצְוָה. מָה שֶׁכָּתַבְתִּי לְמַעְלָה בְּמִצְוָה רס"ו (רסג) בְּסֵדֶר זֶה, שֶׁעִנְיַן הַטֻּמְאָה רָאוּי לְהִתְרַחֵק מִן הַכֹּהֲנִים שֶׁהֵם קְדוֹשִׁים עוֹשֵׂי מְלֶאכֶת הַשֵּׁם יִתְבָּרַךְ תָּמִיד, וְהַכֹּהֵן הַגָּדוֹל הַנִּבְדָּל לִהְיוֹת קֹדֶשׁ קָדָשִׁים, עִם הֱיוֹתוֹ בַּעַל גּוּף נַפְשׁוֹ תִּשְׁכֹּן תָּמִיד בְּתוֹךְ הַמְשָׁרְתִים הָעֶלְיוֹנִים, עַל כֵּן לֹא תָּחוּשׁ הַתּוֹרָה עָלָיו לְהַתִּיר לוֹ טֻמְאָה לְעוֹלָם, וַאֲפִילּוּ בַּקְּרוֹבִים כְּמוֹ לְכֹהֲנִים הֶדְיוֹטִים שֶׁכָּתַבְתִּי לְמַעְלָה (מצוה רסג) דְּחָס רַחֲמָנָא עֲלֵיהֶם, שֶׁיִּשְׁפְּכוּ נַפְשָׁם בְּבֵית הַמֵּת כִּי יֵחַם לְבָבָם עַל קְרוֹבֵיהֶם, מָה שֶׁאֵינוֹ כֵּן בַּכֹּהֵן הַגָּדוֹל, כִּי מֵרֹב דְּבֵקוּת נַפְשׁוֹ לְמַעְלָה יִתְפַּשֵּׁט לְגַמְרֵי מִטֶּבַע בְּנֵי אִישׁ וְיַשְׁכִּיחַ מִלִּבּוֹ כָּל עֵסֶק עוֹלָם הַזֶּה הַנִּפְסָד, וְעַל חֶבְרַת הַקָּרוֹב לֹא תִּבְכֶּה נַפְשׁוֹ, כִּי כְּבָר הוּא נִפְרַד מִמֶּנּוּ בְּעוֹדֶנּוּ בַּחַיִּים. וּבְדִינֵי טֻמְאַת הַמֵּת וְאֹהֶל הַמֵּת דִּבַּרְתִּי מְעַט כְּמִנְהָגִי בְּסֵדֶר זֶה, אֵין רָאוּי לְהַחְזִירוֹ פֶּן יִכְבַּד עַל הַקּוֹרֵא. [הלכות אבל פ"ג].
What I wrote above in Mitzvah 266 in this Order (Sefer HaChinukh 263) is from the roots of the commandment — that it is fitting to distance the priests, who are the holy ones who do the service of God, from the matter of impurity. And [regarding] the high priest who is distinguished to be Holy of Holies; though he has a body, his soul always dwells among the elevated servants. Therefore, the Torah is not concerned to ever permit him impurity — even for the relatives which the Torah is concerned about for the ordinary priests, which I wrote about above (Sefer HaChinukh 263), who will pour out their souls in the house of [mourning] because their hearts are heated for their relatives. The high priest, by contrast, is thoroughly bound to loftier pursuits and entirely separate from human nature. He will lose any memory of this fleeting world; he will not weep for the loss of one of his society because he was already apart from them in life. As far as the laws of impurity from the dead and the tent of the dead, I have already spoken some according to my custom in this Order; it is not fitting to repeat it, lest it become burdensome for the reader. (See Mishneh Torah, Laws of Mourning 3.)
וְנוֹהֵג אִסּוּר זֶה בִּזְמַן הַבַּיִת שֶׁיֵּשׁ שָׁם כֹּהֵן גָּדוֹל וּבְכָל מָקוֹם שֶׁיִּהְיֶה, וַאֲפִלּוּ אִם הָיָה מִקְרֶה שֶׁיָּצָא לְחוּצָה לָאָרֶץ מֻזְהָר מֵהִכָּנֵס בְּאֹהֶל הַמֵּת. וְאִם עָבַר וְנִכְנַס שָׁם בְּמֵזִיד וַאֲפִלּוּ אָבִיו אוֹ אִמּוֹ מֵתִים בַּבַּיִת לוֹקֶה.
And this prohibition is practiced at the time of the [Temple] when there was a High Priest there. And in any place that he may be — even if on some occasion he exited the Land — he is [still forbidden] from entering into the tent of a dead body. And if he transgressed and entered there volitionally — even [if it was] his father or mother [that] were dead in the house — he is lashed.