נִּבְלַת הָעוֹף הַטָּהוֹר מְטַמָּא מִן הַתּוֹרָה. מִפִּי הַשְּׁמוּעָה לָמְדוּ שֶׁזֶּה שֶׁנֶּאֱמַר (ויקרא יז טו) "וְכָל נֶפֶשׁ אֲשֶׁר תֹּאכַל נְבֵלָה וּטְרֵפָה בָּאֶזְרָח וּבַגֵּר וְכִבֶּס בְּגָדָיו וְרָחַץ בַּמַּיִם" אֵינוֹ מְדַבֵּר אֶלָּא בְּאוֹכֵל נִבְלַת הָעוֹף הַטָּהוֹר בִּלְבַד שֶׁהוּא אָסוּר מִשּׁוּם נְבֵלָה וּטְרֵפָה. וְכֵיצַד הִיא טֻמְאָתָהּ. אֵינָהּ מְטַמְּאָה לֹא בְּמַגָּע וְלֹא בְּמַשָּׂא וְלֹא כְּשֶׁהִיא בְּתוֹךְ הַפֶּה אֶלָּא בְּתוֹךְ בֵּית הַבְּלִיעָה. שֶׁנֶּאֱמַר וְכָל נֶפֶשׁ אֲשֶׁר תֹּאכַל אֵינָהּ מְטַמְּאָה אֶלָּא כְּשֶׁהִיא בְּבֵית הַנֶּפֶשׁ. וְזֶה שֶׁנֶּאֱמַר תֹּאכַל לָתֵת שִׁעוּר לְטֻמְאָתָהּ כְּשִׁעוּר אֲכִילָה שֶׁהוּא כְּזַיִת. וַהֲרֵי נֶאֱמַר בָּהּ וְכִבֶּס בְּגָדָיו מְלַמֵּד שֶׁהַמִּתְטַמֵּא בָּהּ מְטַמֵּא בְּגָדָיו עַד שֶׁיִּפְרשׁ מִמְּטַמְּאָיו כְּמוֹ שֶׁבֵּאַרְנוּ. כֵּיצַד. הַבּוֹלֵעַ כְּזַיִת מִנִּבְלַת הָעוֹף הַטָּהוֹר וְנָגַע בְּכֵלִים בִּשְׁעַת בְּלִיעָתוֹ טְמֵאִים וְנַעֲשׂוּ רִאשׁוֹן לְטֻמְאָה. הָיָה נוֹגֵעַ בְּאָדָם וּבִכְלֵי חֶרֶס בִּשְׁעַת בְּלִיעָתוֹ לֹא טִמְּאָן כְּמוֹ שֶׁבֵּאַרְנוּ בִּשְׁאָר אֲבוֹת הַטֻּמְאוֹת. וְאַחַר שֶׁבָּלַע אֵינוֹ מְטַמֵּא שְׁאָר כֵּלִים שֶׁהֲרֵי הוּא כִּכְלִי רִאשׁוֹן לְטֻמְאָה אַחַר שֶׁפֵּרֵשׁ מִמְּטַמְּאָיו שֶׁאַף עַל פִּי שֶׁהוּא טָעוּן טְבִילָה וְהַעֲרֵב שֶׁמֶשׁ אֵינוֹ מְטַמֵּא כֵּלִים:
The carcass of a kosher fowl that was not ritually slaughtered imparts impurity according to Scriptural Law. According to the Oral Tradition, it is taught that Leviticus 17:15: "Any soul that will partake of the carcass of a fowl or one that is tereifah - whether a native or a convert - shall launder his garments and bathe in water" is speaking only about one who partakes of the carcass of a fowl from a kosher species that is forbidden because it is a carcass or tereifah. How is its impurity defined? It does not impart impurity when touched or when carried or when it is in one's mouth, only in one's gullet. This is implied by the phrase: "Any soul that will partake...," i.e., it imparts impurity only when it has been ingested in "the chamber of the soul." It uses the term "partake" to define that the minimum measure that imparts impurity is the measure to which the prohibition against eating applies, i.e., an olive-sized portion. Moreover, it is written: "shall launder his garments;" this teaches that one who contracts impurity from such a carcass imparts impurity to his garments until he separates himself from the object that imparted impurity to him, as we explained. What is implied? When one swallows an olive-sized portion of the carcass of a fowl from a kosher species and touched keilim while swallowing it, they become impure and are considered a primary derivative of impurity. If he was touching a person or earthenware containers while swallowing it, he does not impart impurity to them, as we stated with regard to other primary categories of impurity. After he has ingested the meat from the fowl, he does not impart impurity to other keilim. He is like a k'li that is a primary derivative of impurity that has been separated from the substance that imparted impurity to him. For even though he must immerse himself and wait for nightfall to regain ritual purity, he does not impart impurity to keilim.
