סימן קא סעיף ג
נָכְרִי שֶׁהֵבִיא בְּיוֹם טוֹב רִאשׁוֹן דָּגִים אוֹ פֵּרוֹת שֶׁיֵּשׁ לָחוּשׁ שֶׁמָּא נִצּוֹדוּ הַיּוֹם אוֹ נִתְלְשׁוּ הַיּוֹם, אוֹ הוּבְאוּ מִחוּץ לַתְּחוּם, אֲסוּרִים הַיּוֹם בְּטִלְטוּל, וְלָעֶרֶב מֻתָּרִים. שֶׁאִם הָאֵינוֹ יְהוּדִי מַכִּירוֹ וְנוֹתְנָם לוֹ בְּלֹא קְצִיצַת דָּמִים, מֻתָּר לְקַחְתָּם וּלְאָכְלָם (וְעַיֵּן עוֹד בְּסִימָן צ"ט סָעִיף ב' וְתִלְמַד לְכָאן) חוּץ מִיּוֹם טוֹב שֶׁל רֹאשׁ הַשָּׁנָה, שֶׁאֲפִלּוּ הוּבְאוּ בְּיוֹם רִאשׁוֹן, אֲסוּרִים בְּיוֹם שֵׁנִי.
If a non-Jew brings fish or fruit on the first day of Yom Tov, and there is reason to suspect that the fish were caught, or the fruit was picked on that day, or brought in from outside the Techum,7See glossary and Chapter 65. If the non-Jew is living in your city and is known to have the items in stock within the techum, you may assume what he has brought is from within the techum. (Shulchan Aruch 515:7) it is forbidden to handle them on that day. In the evening on the second night of Yom Tov8Immediately after nightfall. (Mishnah Berurah 515:59) it is permitted to use them. Thus, if the non-Jew knows you, and gives them to you without quoting a price, you may take them and eat them; except on Rosh Hashanah, when, even if they were brought on the first day, they are forbidden on the second day.9This refers only to where it may have been harvested or caught on that day for these are melachos. But if there is only concern that they may have been brought in from outside the techum, they are permitted on the second day, even if they were brought for a Jew and even if it is Rosh Hashanah or Shabbos, but you must wait for the time it would take the non-Jew to bring it from that place after nightfall.(see Shulchan Aruch 515:8, Vilna Gaon, Mishna Berurah 515:66)
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.)