Halakhah for Bekhorot 1:1
הַלּוֹקֵחַ עֻבַּר חֲמוֹרוֹ שֶׁל נָכְרִי, וְהַמּוֹכֵר לוֹ אַף עַל פִּי שֶׁאֵינוֹ רַשַּׁאי, וְהַמִּשְׁתַּתֵּף לוֹ, וְהַמְקַבֵּל מִמֶּנּוּ, וְהַנּוֹתֵן לוֹ בְקַבָּלָה, פָּטוּר מִן הַבְּכוֹרָה, שֶׁנֶּאֱמַר (במדבר ג), בְּיִשְׂרָאֵל, אֲבָל לֹא בַאֲחֵרִים. כֹּהֲנִים וּלְוִיִּם פְּטוּרִין מִקַּל וָחֹמֶר, אִם פָּטְרוּ שֶׁל יִשְׂרָאֵל בַּמִּדְבָּר, דִּין הוּא שֶׁיִּפְטְרוּ שֶׁל עַצְמָן:
If one buys an unborn donkey fetus from a non-Jew, sells [an unborn donkey fetus] to [a non-Jew] even though one does not have permission to, has a partnership with [a non-Jew], receives [an unborn donkey fetus] from [a non-Jew], or gives [an unborn donkey fetus] to [a non-Jew], [the unborn donkey fetus] is exempt from the laws of the first-born. As it is written (Numbers 3:13): "in Israel", but not by others. Priests and Levites are also exempt, for if they could exempt a Israelite [while the Jewish people were] in the desert, then they would certainly exempt themselves.