Jerusalem Talmud Bava Metzia 7:7

משנה: זְאֵב אֶחָד אֵינוֹ אוֹנֶס וּשְׁנֵי זְאֵיבִין אוֹנֶס. רִבִּי יְהוּדָה אוֹמֵר בְּשָׁעַת מִשְׁלַחַת זְאֵבִים אַף זְאֵב אֶחָד אוֹנֶס. שְׁנֵי כְלָבִים אֵינָן אוֹנֶס. יַדּוּעַ הַבַּבְלִי אוֹמֵר מִשּׁוּם רִבִּי מֵאִיר. מֵרוּחַ אַחַת אֵינוֹ אוֹנֶס מִשְׁתֵּי רוּחוֹת אוֹנֶס. הַלִּיסְטִין הֲרֵי הֶן אוֹנֶס. הָאֲרִי וְהַדּוֹב וְהַנָּמֵר וְהַבַּרְדְּלִיס וְהַנָּחָשׁ הֲרֵי אֵילּוּ אוֹנְסִין. אֵימָתַי בִּזְמַן שֶׁבָּאוּ מֵאֵילֵיהֶן אֲבָל אִם הוֹלִיכָן לִמְקוֹם גְּדוּדֵי חַיָּה וְלִיסְטִין אֵין אֵילּוּ אוֹנְסִין. מֵתָה כְדַרְכָּהּ הֲרֵי זֶה אוֹנֶס. סִכְפָּהּ וָמֵתָה אֵינוֹ אוֹנֶס. עָלָת לְרָאשֵׁי צוּקִין וְנָֽפְלָה הֲרֵי זֶה אוֹנֶס. הֶעֱלָהּ לְרָאשֵׁי צוּקִין וְנָֽפְלָה אֵינוֹ אוֹנֶס. מַתְנֶה שׁוֹמֵֵר חִנָּם לִהְיוֹת פָּטוּר מִשְּׁבוּעָה וְהַשּׁוֹאֵל לִהְיוֹת פָּטוּר מִלְּשַׁלֵּם נוֹשֵׂא שָׂכָר וְהַשּׂוֹכֵר לִהְיוֹת פְּטוּרִין מִשְּׁבוּעָה וּמִלְּשַׁלֵּם. כָּל־הַמַּתְנֶה עַל מַה שֶׁכָּתוּב בַּתּוֹרָה תְּנָייוֹ בָטֵל. וְכָל־תְּנַאי שֶׁהוּא מַעֲשֶׂה בִתְחִילָּתוֹ תְּנָייוֹ בָטֵל. וְכָל־שֶׁאֶיפְשָׁר לוֹ לְקַייְמוֹ בְסוֹפוֹ וְהִתְנָה עָלָיו מִתְּחִילָּתוֹ תְּנָייוֹ קַייָם. MISHNAH: ⁵¹The next four Mishnaiot deal with the responsibilities of the paid keeper and the renter, who may free themselves from paying for an unavoidable accident by swearing but have to pay for avoidable accidents. The prime example of the paid keeper is the shepherd, for whom these rules are formulated. One wolf is not an unavoidable accident, two wolves are. Rebbi Jehudah says, in times when wolves appear in packs, even a single wolf is an unavoidable accident.
Two dogs are not an unavoidable accident. Yaddua the Babylonian says in the name of Rebbi Meїr: From the same direction it is not an unavoidable accident; from two different directions it is an unavoidable accident
Robbers are an unavoidable accident. A lion, and a bear, and a leopard, and a panther⁵²Greek πάρδαλις, Latin pardalis., and a snake are unavoidable accidents. When? If they came by themselves. But if he led [the flock] to a place of troops of wild animals or robbers, these are not unavoidable accidents.
If [an animal] dies a natural death it is an unavoidable accident. If he tortured it and it died, it is not an unavoidable accident. If it climbed to the top of a cliff and fell, it is an unavoidable accident. If he led it onto the top of a cliff and it fell, it is not an unavoidable accident. The unpaid keeper may stipulate that he be free from swearing, the borrower that he not be liable to pay, the paid keeper and the renter that they not be liable to swear or to pay⁵³In money matters there is freedom in contracting. Even though the rules of responsibility of keepers are biblical (Notes 44,45), they are default rules to be used in the absence of contrary stipulations. It follows that Mishnah 14 deals only with stipulations other than money matters..
The stipulation of anybody who stipulates against what is written in the Torah is invalid. Any stipulation which follows a prior action is invalid⁵⁴An action cannot be invalidated retroactively. If a man preliminarily marries a woman and after that tries to impose conditions on the act, he remains unconditionally married.. But any stipulation which it is possible to fulfill at the end and he stipulated it at the start is valid⁵⁵But any condition which was intended to be impossible to keep is void. If a man divorces his wife saying, this is your letter of divorce on condition that you cross the ocean on your feet, or that you fly in the air like a bird, she is unconditionally divorced (Tosephta Giṭṭin 5:12)..

הלכה: זְאֵב אֶחָד אֵינוֹ אוֹנֶס כול׳. כָּל־הַמַּתְנֶה עַל מַה שֶׁכָּתוּב בַּתּוֹרָה כול׳. תַּנֵּי. כָּל־הַמַּתְנֶה עַל מַה שֶׁכָּתוּב בַּתּוֹרָה. תְּנַאי מָמוֹן תְּנָאוֹ קַייָם. תְּנַאי שֶׁאֵינוֹ שֶׁלְּמָמוֹן תְּנָאוֹ בָטֵל. כֵּיצַד. אָמַר לְאִשָׁה. הֲרֵי אַתְּ מְקוּדֶּשֶׁת לִי עַל מְנָת שֶׁאֵין לִיךְ עָלַי שְׁאֵר כְּסוּת וְעוֹנָה. הֲרֵי זוֹ מְקוּדֶּשֶׁת [וּתְנָייוֹ קַייָם. עַל מְנָת] שֶׁאִם מֵתִי לֹא תְהֵא זְקוּקָה לְיִיבּוּם. הֲרֵי זוֹ מְקוּדֶּשֶׁת וּתְנָאוֹ בָטֵל. HALAKHAH: “One wolf is not an unavoidable accident,” etc. “The stipulation of anybody who stipulates against what is written in the Torah,” etc. It was stated: ⁵⁶Tosephta Qiddušin 3:8; cf. Kiddushin 1:2:25" href="/Jerusalem_Talmud_Kiddushin.1.2.25">Qiddušin 1:2, Notes 262–271 (Kiddushin.19b">Babli Qiddušin 19b).“The stipulation of anybody who stipulates against what is written in the Torah, monetary stipulations are valid, nonmonetary stipulations are invalid.” How is this? If one said to a woman: be preliminarily married to me on condition that you have no claim on me for sustenance, clothing, and marital relations, she is preliminarily married [and his stipulation is valid. “On condition]⁵⁷Addition from E, missing in L. The addition is unquestionably correct even though it is pointed out in Kiddushin 1:2:25" href="/Jerusalem_Talmud_Kiddushin.1.2.25">Qiddušin 1:2 (Note 268) that only the first two conditions are of monetary character. There, the problem is explained away by restricting the possibility of such a condition to preliminary marriage with a very young girl who is not available for sexual relations. But from the story of R. Tarphon who in times of famine preliminarily married 300 women to give them access to heave (Yevamot 4:12:5" href="/Jerusalem_Talmud_Yevamot.4.12.5">Yebamot4:12 Note 197; Tosephta Ketubot 5:1) and certainly did not offer them sustenance and clothing from his own means, it seems that if some of the conditions are of monetary character and the nonmonetary stipulation is not operative at the moment (since marital relations are obligatory and permitted only after definitive marriage), the stipulation is valid and if it is valid at the moment it is made it remains valid even after the nonmonetary stipulation becomes operative. that it I die you shall not be obligated for levirate marriage, she is preliminarily married but his stipulation is invalid.”

זֶה הַכְּלָל שֶׁהָיָה רִבִּי יוּדָה בֶן תֵּימָא אוֹמֵר. כֵּל־דָּבָר שֶׁאֵיפְשָׁר לְהִתְקַייֵם וְהִתְנָה עִמָּהּ לֹא נִתְכַּװֵן אֶלָּא לְהַפְלִיגָהּ. בֵּין שֶׁאָמַר בִּכְתָב בֵּין שֶׁאָמַר בְּפֶה. כָּל־הַמִּתְקַייֵם בְּפֶה מִתְקַייֵם בִּכְתָב. וּכְפַר עוֹתְנַי כְּגָלִיל וְאַנְטִיפַּטְרִס כִּיהוּדָה. אֶת שֶׁבֵּנְתַיִים מַטִּילִין אוֹתוֹ לְחוּמְרוֹ. ⁵⁸Tosephta Giṭṭin 5:12; Babli 94a, Gittin.84a">Giṭṭin 84a; cf. Tosefta kiFshutah Giṭṭin pp. 886–887.“This is the principle enunciated by Rebbi Jehudah ben Tema: Anything which is impossible to keep but he stipulated for her only to put her off^55,But any condition which was intended to be impossible to keep is void. If a man divorces his wife saying, this is your letter of divorce on condition that you cross the ocean on your feet, or that you fly in the air like a bird, she is unconditionally divorced (Tosephta Giṭṭin 5:12).⁵⁹The majority opinion in the Tosephta and the Babli holds that a bill of divorce given with an impossible stipulation is invalid.. Whether we put it in writing or said it orally, everything valid orally is valid when written⁶⁰In general, conditions written into a bill of divorce invalidate the entire bill. Cf. Gittin 3:1:6" href="/Jerusalem_Talmud_Gittin.3.1.6">Giṭṭin 3:1, Notes 40–56.”. ⁶¹Tosephta Giṭṭin 5:7; Gittin.76a">Babli Giṭṭin76a. This refers to a man who before departing gave his wife a bill of divorce and stated that she should be divorced if he left Judea, or if he reached Galilee, etc. On the via maris Antipatris (near Petaḥ Tiqwah) was the border station in Judea and Kefar Othnay (Kafr Uthnay near Megiddo) the border station in Galilee; Gittin 7:7:1" href="/Jerusalem_Talmud_Gittin.7.7.1">Mishnah Giṭṭin 7:8.“And Kefar Othnay belongs to Galilee, Antipatris to Judea; the places in between are interpreted stringently⁶²Since the position of the stretch of the via maris passing through Samaria is indeterminate in halakhah, if the husband, e. g., left Judea but did not reach Galilee the wife is “divorced and not divorced.”.”