הלכות חמץ ומצה ב׳Leavened and Unleavened Bread 2

Halacha 1א׳

מִצְוַת עֲשֵׂה מִן הַתּוֹרָה לְהַשְׁבִּית הֶחָמֵץ קֹדֶם זְמַן אִסּוּר אֲכִילָתוֹ שֶׁנֶּאֱמַר (שמות יב טו) "בַּיּוֹם הָרִאשׁוֹן תַּשְׁבִּיתוּ שְּׂאֹר מִבָּתֵּיכֶם". וּמִפִּי הַשְּׁמוּעָה לָמְדוּ שֶׁבָּרִאשׁוֹן זֶה הוּא יוֹם אַרְבָּעָה עָשָׂר. רְאָיָה לְדָבָר זֶה מַה שֶּׁכָּתוּב בַּתּוֹרָה (שמות לד כה) "לֹא תִשְׁחַט עַל חָמֵץ דַּם זִבְחִי" כְּלוֹמַר לֹא תִּשְׁחַט הַפֶּסַח וַעֲדַיִן הֶחָמֵץ קַיָּם. וּשְׁחִיטַת הַפֶּסַח הוּא יוֹם אַרְבָּעָה עָשָׂר אַחַר חֲצוֹת:

It is a positive commandment of the Torah to remove the leaven before the time when eating it is forbidden, as it is said (Exodus 12:15), "On the first day you shall put away leaven out of your houses." And from tradition they learned that this first day is the fourteenth. The proof of this matter is what is written in the Torah (Exodus 34:25), "You shall not slaughter the blood of My sacrifice with leaven" — as if to say: you shall not slaughter the Passover offering while the leaven is still in being. And the slaughtering of the Passover offering is on the fourteenth day after midday.

Halacha 2ב׳

וּמַה הִיא הַשְׁבָּתָה זוֹ הָאֲמוּרָה בַּתּוֹרָה הִיא שֶׁיְּבַטֵּל הֶחָמֵץ בְּלִבּוֹ וְיַחֲשֹׁב אוֹתוֹ כְּעָפָר וְיָשִׂים בְּלִבּוֹ שֶׁאֵין בִּרְשׁוּתוֹ חָמֵץ כְּלָל. וְשֶׁכָּל חָמֵץ שֶׁבִּרְשׁוּתוֹ הֲרֵי הוּא כְּעָפָר וּכְדָבָר שֶׁאֵין בּוֹ צֹרֶךְ כְּלָל:

And what is this removal that is spoken of in the Torah? It is that he nullify the leaven in his heart and account it as dust, and set it in his heart that there is no leaven at all in his possession, and that all the leaven that is in his possession is as dust and as a thing for which there is no need at all.

Halacha 3ג׳

וּמִדִּבְרֵי סוֹפְרִים לְחַפֵּשׂ אַחַר הֶחָמֵץ בַּמַּחֲבוֹאוֹת וּבַחוֹרִים וְלִבְדֹּק וּלְהוֹצִיאוֹ מִכָּל גְּבוּלוֹ. וְכֵן מִדִּבְרֵי סוֹפְרִים שֶׁבּוֹדְקִין וּמַשְׁבִּיתִין הֶחָמֵץ בַּלַּיְלָה מִתְּחִלַּת לֵיל אַרְבָּעָה עָשָׂר לְאוֹר הַנֵּר. מִפְּנֵי שֶׁבַּלַּיְלָה כָּל הָעָם מְצוּיִין בַּבָּתִּים וְאוֹר הַנֵּר יָפֶה לִבְדִיקָה. וְאֵין קוֹבְעִין מִדְרָשׁ בְּסוֹף יוֹם שְׁלֹשָׁה עָשָׂר. וְכֵן הֶחָכָם לֹא יַתְחִיל לִקְרוֹת בְּעֵת זוֹ שֶׁמָּא יִמָּשֵׁךְ וְיִמָּנַע מִבְּדִיקַת חָמֵץ בִּתְחִלַּת זְמַנָּה:

By rabbinic enactment, one must search for ḥametz in hiding-places and holes, and remove it from his entire domain. Also, by rabbinic enactment, one should search and remove the ḥametz by lamplight at night, at the beginning of the night preceding the fourteenth day of Nisan, because all the people are then at home and lamplight is best for searching. And we do not fix study at the end of the thirteenth day [of Nissan]. And likewise should a sage not begin to read at that time, lest he be drawn [by it] and be prevented from searching for chamets at the beginning of its time.