סימן קעז סעיף טו
מִצְוָה לִמְכֹּר לַגּוֹי אֶת הַבְּהֵמָה הַטְּהוֹרָה אוֹ לְהִשְּׁתַּתֵּף עִמוֹ בָּהּ קֹדֶם שֶׁתֵּלֵד, כְּדֵי לְפָטְרָהּ מֵהַבְּכוֹרָה. וְאַף עַל פִּי שֶׁמַּפְקִיעַ קְדֻשַּׁת הַבְּכוֹר, הָכִי עָדִיף טְפֵי, שֶׁלֹּא יָבוֹא לִדֵי מִכְשׁוֹל בְּגִזָּה וַעֲבוֹדָה. וְאִם יַקְנֶה לַגּוֹי אֶת הָעֻבָּר, לֹא מַהֲנֵי, כֵּיוָן דַּהֲוֵי דָבָר שֶׁלֹא בָא לָעוֹלָם, אֶלָּא צָרִיךְ לְהַקְנוֹת לוֹ אֶת הָאֵם. וְהַקִּנְיָן יהְיֶה בְּאֹפֶן זֶה, יִשְׁתַּוֶּה עִם הַגּוֹי עַל מְחִיר הַפָּרָה, וְגַם יַשְׂכִּיר לוֹ אֶת הַמָּקוֹם אֲשֶר הַפָּרָה עוֹמֶדֶת שָׁם, וְהַגּוֹי יִתֵּן לוֹ פְּרוּטָה, וְיֹאמַר לוֹ הַיִשְֹרָאֵל, בְּזוֹ הַפְּרוּטָה, תִּקְנֶה אֶת הַמָּקוֹם אֲשֶׁר הַפָּרָה עוֹמֶדֶת שָׁמָּה, וְהַמָּקוֹם הַזֶּה יַקְנֶה לְךָ אֶת הַפָּרָה. אוֹ יַעֲשֶׂה כֵּן, שֶׁלְּאַחַר שֶׁהִשְׁתַּוּוּ עַל מְחִיר הַפָּרָה, יִתֶּן לוֹ הַגּוֹי פְּרוּטָה, וְגַם יִמְשֹׁךְ הַגּוֹי אֶת הַפָּרָה לִרְשׁוּתוֹ אוֹ לְסִמְטָא, וְקוֹנֶה אוֹתָהּ בִּמְשִׁיכָה וּמָעוֹת. וַאֲפִלּוּ אִם מַחֲזִירָהּ אַחַר כָּךְ לִרְשׁוּת יִשְֹרָאֵל, לֹא אִכְפַּת לָן.
It is a mitzvah to sell to a Gentile the clean animal (before it gives birth), or to form a partnership with him before it gives birth, in order to exempt it from the laws of the firstborn.8This applies only now, since there is no Beis Hamikdash. ( Taz 320:5) And although (by doing this), it circumvents the holiness of the firstborn, it is, nevertheless, preferable so that no violations will be committed with regard to its wool and its use for work. Transferring the title (of the calf) to the Gentile when the calf is yet unborn is of no avail, since it is something that has not come into existence;9Therefore, transfer of ownership cannot be accomplished. but the title of the mother must be transferred as well. The transfer of the title should be done in this manner: the owner should come to terms with the Gentile regarding the price of the cow, and also rent him the place that the cow now occupies; the Gentile should give him a perutah,10A perutah was a coin of minimal value. and the Jew should say to him, "With this perutah you shall acquire the place that the cow now occupies, and this place will acquire the title of the cow for you.11The yard thus acquires its own contents for its owner. This is called kinyan chatzer. It can also be done in this manner: after they come to terms about the price of the cow, the Gentile should give him a perutah, and then lead the cow into his own premises, or into an alleyway, whereby he acquires title both by meshicha (actual transfer) and with money. Even if he returns the cow afterwards to the premises of the Jew it does not matter.
תנא דבי אליהו כל השונה הלכות בכל יום מובטח לו שהוא בן העולם הבא שנאמר הליכות עולם לו אל תקרי הליכות אלא הלכות (נדה ע"ג.)