אורח חיים רמ״זOrach Chayim 247

Se’if 1א׳

שׁוֹלֵחַ אָדָם אִגֶּרֶת בְּיַד עַכּוּ"ם, וַאֲפִלּוּ בְּעֶרֶב שַׁבָּת עִם חֲשֵׁכָה; וְהוּא שֶׁקָּצַץ לוֹ דָּמִים, וּבִלְבַד שֶׁלֹּא יֹאמַר לוֹ שֶׁיֵּלֵךְ בְּשַׁבָּת; וְאִם לֹא קָצַץ, אִי לֹא קָבִיעַ בֵּי דֹּאַר (פֵּרוּשׁ אִישׁ יָדוּעַ שֶׁכָּל כְּתָב אֵלָיו יוּבַל וְהוּא מְשַׁלְּחַם לְמִי שֶׁשָּׁלוּחַ אֵלָיו). בְּמָתָא, אָסוּר לִשְׁלֹחַ אֲפִלּוּ מִיּוֹם רִאשׁוֹן; וְאִי קָבִיעַ בֵּי דֹּאַר בְּמָתָא, מְשַׁלְּחָן אֲפִלּוּ בְּעֶרֶב שַׁבָּת וְהוּא שֶׁיְּהֵא שְׁהוּת בַּיּוֹם כְּדֵי שֶׁיּוּכַל לְהַגִּיעַ לַבַּיִת הַסָמוּךְ לַחוֹמָה. הַגָּה: וְיֵשׁ מַתִּירִין אֲפִלּוּ לֹא קָצַץ, וַאֲפִלּוּ לֹא קָבִיעַ בֵּי דֹּאַר בְּמָתָא, אִם מְשַׁלְּחוֹ בְּיוֹם ה' אוֹ קֹדֶם לָכֵן; (טוּר) וְיֵשׁ לִסְמֹךְ עֲלַיְיהוּ אִם צְרִיכִים לְכָךְ.

(1) A letter may be sent with a non-Jew even on the eve of Shabbat close to dark, [provided] he specified his wages and he doesn't tell him to travel on Shabbos and if he did not specify [wages], if there is not an established Ba'y Do'ar (meaning, a person about whom it is known to send letters to him and he delivers the letters to their addresses) in town, it is forbidden to send the letter even from Sunday and if there is an established Ba'y Do'ar in town, he may send it even on the eve of Shabbat, provided there is enough time remaining in the day that he is able to reach the house adjacent to the city wall. RAMA: There are those [authorities] who permit this even if he did not specify the wages and there is not an established Ba'y Do'ar in town provided he sends it on Thursday or prior to this and there is basis to rely on this if necessary.

Se’if 2ב׳

אִם הִתְנָה עִמּוֹ שֶׁיִּתֵּן לוֹ שְׂכָרוֹ, אַף עַל פִּי שֶׁלֹּא פֵּרֵשׁ כַּמָּה יִתֵּן לוֹ, דִּינוֹ כְּקוֹצֵץ, דְּסַמְכָא דַּעְתֵּיהּ דְּעַכּוּ"ם וּבְדִידֵיהּ קָא טָרַח; אֲבָל בִּסְתָם, אַף עַל פִּי שֶׁיֵּשׁ בְּדַעְתּוֹ שֶׁיִּתֵּן לוֹ שָׂכָר, אָסוּר, דְּלָא סַמְכָא דַּעְתֵּיהּ וּבִדְיִשְׂרָאֵל קָא טָרַח.

(2) If he stipulated with him that he will give him wages, even though he didn’t say how much he’ll give him, the law is like they set a price, since the non-Jew is working for his sake. But if he didn’t mention it, even though his intention is that he’ll give him wages, it is forbidden since he isn’t depending on it and is working for the sake of the Jew.

Se’if 3ג׳

אִם שְׂכָרוֹ לְיָמִים דָּבָר קָצוּב בְּכָל יוֹם בַּהֲלִיכָתוֹ וּבַחֲזָרָתוֹ, אֶלָּא שֶׁאֵינוֹ מַקְפִּיד עִמּוֹ מָתַי יֵלֵךְ; אִם הוּא בְּעֶרֶב שַׁבָּת, אָסוּר, דִּכְשֶׁיּוֹצֵא בְּשַׁבָּת נִרְאֶה כְּאִלּוּ הִתְנָה עִמּוֹ כָּךְ.

(3) If he employs him daily, something fixed every day when he travels and when he returns, but he isn't particular with him regarding when he travels, if it’s the eve of Shabbat then it’s forbidden because it’s considered like Shabbat [and] it appears he stipulated with him about it.