All males are commanded to appear in Jerusalem at the Temple three times yearly—Pesach, Shavuot, and Sukkot—bringing themselves and their sons who can walk; this mitzvah includes bringing a burnt-offering called olat reiah (requiring no minimum measure, even a dove suffices), and its purpose is for all Israel to internalize through the sacrifice that they are God's chosen people and inheritance, obligated to guard His testimonies.
לְהֵרָאוֹת בָּרְגָלִים בְּבֵית הַבְּחִירָה – שֶׁנִּצְטַוִּינוּ לְהֵרָאוֹת כָּל זָכָר בִּירוּשָׁלַיִם בְּבֵית הַבְּחִירָה שָׁלֹשׁ פְּעָמִים קְבוּעִים בַּשָּׁנָה. וְהֵן, פֶּסַח וְשָׁבוּעוֹת וְסֻכּוֹת, וְעַל זֶה נֶאֱמַר (דברים טז טז) שָׁלֹשׁ פְּעָמִים בַּשָּׁנָה יֵרָאֶה כָל זְכוּרְךָ אֶת פְּנֵי יְיָ אֱלֹהֶיךָ. וְעִנְיַן הַמִּצְוָה, שֶׁיַּעֲלֶה כָּל אָדָם עִם כָּל בֵּן זָכָר שֶׁיֵּשׁ לוֹ שֶׁיּוּכַל לָלֶכֶת לְבַדּוֹ בְּרַגְלָיו לַמִּקְדָּשׁ וְיִתְרָאֶה שָׁם. וּמֵחִיּוּב רְאִיָּה זוֹ, שֶׁיַּקְרִיב שָׁם קָרְבַּן עוֹלָה, וְזֶה הַקָּרְבָּן נִקְרָא עוֹלַת רְאִיָּה וְאֵין לְקָרְבָּן זֶה שִׁעוּר, אֲפִילּוּ תּוֹר אֶחָד אוֹ גּוֹזָל פּוֹטֵר. וּכְבָר כָּתַבְתִּי בְּמִשְׁפָּטִים בְּמִצְוַת לָחֹג בָּרְגָלִים (מצוה פח), מָה שֶׁאָמְרוּ זִכְרוֹנָם לִבְרָכָה (חגיגה י ב) שָׁלֹשׁ מִצְוֹת נִצְטַוּוּ יִשְׂרָאֵל בָּרֶגֶל, חֲגִיגָה רְאִיָּה, שִׂמְחָה, וְעַל כָּל אַחַת מִשָּׁלֹשׁ מִצְוֹת אֵלּוּ, הָיוּ מְבִיאִין קָרְבָּן, וְנִקְרָאִים, קָרְבַּן חֲגִיגָה, שַׁלְמֵי שִׂמְחָה, עוֹלַת רְאִיָּה. מִשָּׁרְשֵׁי הַמִּצְוָה. לְמַעַן יִרְאוּ כָּל יִשְׂרָאֵל וְיִתְּנוּ אֶל לִבָּם בִּפְעֻלַּת הַקָּרְבָּן הַמְעוֹרֵר הַלְּבָבוֹת, כִּי כֻּלָּם מִקְּטַנָּם וְעַד גְּדוֹלָם חֵלֶק הַשֵּׁם וְנַחֲלָתוֹ, עַם קָדוֹשׁ וְנִבְחַר, נוֹצְרֵי עֵדוּתוֹ, סְגֻלַּת כָּל הָעַמִּים אֲשֶׁר תַּחַת כָּל הַשָּׁמָיִם, לִשְׁמֹר חֻקָּיו וּלְקַיֵּם דָּתוֹ, עַל כֵּן יָבוֹאוּ שָׁלֹשׁ פְּעָמִים בַּשָּׁנָה בֵּית הַשֵּׁם, וְהוּא כְּאָמְרָם עַל דֶּרֶךְ מָשָׁל הִנְנוּ לָאֵל לַעֲבָדִים, נִכְנָסִים וּבָאִים בְּצֵל קוֹרָתוֹ, וּבְחֶזְקָתוֹ סְמוּכִים לָעַד לְעוֹלָם בְּאַהֲבָתוֹ וּבְיִרְאָתוֹ, וְזָר לֹא יָבֹא בְּתוֹכֵנוּ, כִּי אֲנַחְנוּ לְבַדֵּנוּ בְּנֵי בֵּיתוֹ. וְעִם הַמַּעֲשֶׂה הַזֶּה, תִּתְעוֹרֵר דַּעְתֵּנוּ, וְנַכְנִיס בְּלִבֵּנוּ מוֹרָאוֹ, וְנִקְבַּע בְּרַעְיוֹנֵנוּ אַהֲבָתוֹ, וְנִזְכֶּה לְקַבֵּל חַסְדּוֹ וּבִרְכָתוֹ. וּבָא עָלֵינוּ הַחִיּוּב בַּזְּכָרִים לְבַד, כִּי הֵם עִקַּר הַבַּיִת, וְהַטַּף וְהַנָּשִׁים טְפֵלָה לָהֶם, וְעִם הַחְזָקָה בָּהֶם לַעֲבָדִים, נַעֲשֵׂית הַחְזָקָה בְּכָל שֶׁהוּא תַּחַת יָדָם. וּמִזֶּה הַיְּסוֹד, נִתְיַחֲדָה לָנוּ מִצְוָה בְּמֹעֵד שְׁנַת הַשְּׁמִטָּה בְּחַג הַסֻּכּוֹת, לְהַקְהִיל שָׁם הָאֲנָשִׁים וְהַנָּשִׁים וְהַטַּף וְהַגֵּרִים, לְפִי שֶׁאוֹתָהּ הַשָּׁנָה, מְשַׁחְרֶרֶת הַכֹּל וּמַפְקַעַת הַשִּׁעְבּוּד מִכָּל הָחַי מִכָּל בָּשָׂר, לְהָשִׁיב הַכֹּל תַּחַת יַד הָאָדוֹן הַשֵּׁם צְבָאוֹת, וְאָז בְּאוֹתָהּ הַשָּׁנָה, לֹא תּוֹעִיל חֶזְקָתָם לַאֲשֶׁר תַּחְתֵּיהֶם, שֶׁאֵין שֵׁם אַדְנוּת בָּאָרֶץ בָּעֵת הַהִיא. וְעוֹד יֵשׁ עִמָּנוּ טַעַם אַחֵר בְּמִצְוַת הַקָּהָל, נִכְתֹּב אוֹתוֹ בִּמְקוֹמוֹ בְּסֵדֶר אַתֶּם נִצָּבִים בְּעֶזְרַת הַשֵּׁם.
To appear on the festivals in the Choice House: That we were commanded to have all males appear in Jerusalem at the Choice House three set times a year — and they are Pesach, Shavuot and Sukkot. And about this is it stated (Deuteronomy 16:16), “Three times a year all your males shall appear before the Lord, your God.” And the content of the commandment is that every man go up to the Temple and appear there with any male child that he has who is able to walk by himself on his [own] feet. And from this obligation of appearing is also that he sacrifice a burnt-offering there. And this sacrifice is called the burnt-offering of being seen (olat reiah). And there is no measure for this sacrifice — even a dove or a fledgling exempts [one]. And I have already written in Mishpatim on the commandment to celebrate on the festivals (Sefer HaChinukh 88), that which they, may their memory be blessed, said (Chagigah 10b) [that] three commandments were Israel commanded on the holiday: celebration, being seen and joy. And they would bring a sacrifice for each one of these three commandments and they are called the festive sacrifice, the peace-offerings of joy and the burnt-offering of being seen. It is from the roots of the commandment [that it is] in order that all of Israel see and place upon their hearts, through the act of the sacrifice which awakens the hearts, that all of them — from the small to the great — are God’s portion and His inheritance, a holy and chosen people, those that guard His testimonies, the treasure from all the peoples under all of the skies [that] keep His statutes and observe His religion. Hence they come three times a year to the House of God. And it is like their saying metaphorically, “Behold, we are like slaves to God, entering and coming under the shade of His roof, relying upon His strength forever and ever in the love for Him and in the fear of Him; and no foreigner shall come among us, as we alone are the children of His house.” And with this act, our minds are aroused and we place His fear into our hearts and we fix His love into our thoughts, and we merit to receive His kindness and His blessing. And the obligation comes to us only upon the males, since they are the essence of the household, and the children and wives are attached to them; and when there is control over [the males] as slaves, the control is [also] established over all that is under their hand. And from this foundation was the commandment at the appointed time of the sabbatical year during the holiday of Sukkot made unique, to gather there the men, women, children and strangers. As that year liberates all and removes the subjugation from all the living — from all flesh — to return everything back under the hand of the Master, the Lord of Hosts. And then during that year the control over those under them is not effective, as there is no domination in the Land at that time. And there is another reason with us for the commandment of gathering (hakhel) — we shall write it in its place in the Order of Atem Netsavim (Sefer HaChinukh 612) with God’s help.