Reference for Bekhorot 2:1
הַלּוֹקֵחַ עֻבַּר פָּרָתוֹ שֶׁל נָכְרִי, וְהַמּוֹכֵר לוֹ אַף עַל פִּי שֶׁאֵינוֹ רַשַּׁאי, הַמִּשְׁתַּתֵּף לוֹ, וְהַמְקַבֵּל מִמֶּנּוּ, וְהַנּוֹתֵן לוֹ בְקַבָּלָה, פָּטוּר מִן הַבְּכוֹרָה, שֶׁנֶּאֱמַר (במדבר ג), בְּיִשְׂרָאֵל, אֲבָל לֹא בַאֲחֵרִים. כֹּהֲנִים וּלְוִיִּם חַיָּבִין. לֹא נִפְטְרוּ מִבְּכוֹר בְּהֵמָה טְהוֹרָה, (וְלֹא נִפְטְרוּ) אֶלָּא מִפִּדְיוֹן הַבֵּן וּמִפֶּטֶר חֲמוֹר:
If one buys an unborn cow fetus from a non-Jew, sells [an unborn cow fetus] to [a non-Jew] even though one does not have permission to, has a partnership with [a non-Jew], receives [an unborn cow fetus] from [a non-Jew], or gives [an unborn cow fetus] to [a non-Jew], [the unborn cow fetus] is exempt from [the obligations of] the firstborn. As it is written (Numbers 3:13): "in Israel", but not by others. Priests and Levites are obligated, for they were not exempted from [the obligations of] the firstborn of a pure kosher animal, (they were only exempted) from redemption the firstborn son and [the obligations of] the firstborn of a donkey.