Jerusalem Talmud Kiddushin 3.11

משנה: קִידַּשְׁתִּי אֶת בִּתֵּךְ וְהִיא אוֹמֶרֶת לֹא קִידַּשְׁתָּ אֶלָּא אוֹתִי הוּא אָסוּר בִּקְרוֹבוֹת קְטַנָּה וּקְטַנָּה מוּתֶּרֶת בִּקְרוֹבָיו. הוּא מוּתָּר בִּקְרוֹבוֹת גְּדוֹלָה וּגְּדוֹלָה אֲסוּרָה בִּקְרוֹבָיו.

MISHNAH: “I am preliminarily married to your daughter,” but she says, you are only preliminarily married to me; he is forbidden the relatives of the young woman, and the young woman is permitted his relatives; he is permitted the relatives of the old woman, and the old woman is forbidden his relatives.

הלכה: קִידַּשְׁתִּי אֶת בִּתֵּךְ כול׳. רַב חוּנָא אָמַר. מְפַתִּים אוֹתוֹ לִיתֵּן גֵּט וְכוֹפִין אוֹתוֹ לִיתֵּן קְנָס. הַגַּע עַצְמָךְ שֶׁהָיָה חָבֵר וְהָיָה יוֹדֵעַ שֶׁחַיָיב גֵּט וּקְנָס וְהָלַךְ וְנָשָׂא אֶת אֲחוֹתָהּ. מוֹצִיאִין אֶת הַוַודַּאי מִפְּנֵי הַסָּפֵק.

HALAKHAH: “I am preliminarily married to your daughter,” etc. Rav Ḥuna said, one induces him to give a bill of divorce, and one forces him to pay a fine. Think of it, if he was a Fellow and knew that he would be obligated for a bill of divorce and a fine; if he went and married her sister, would one force the divorce of the certain because of the doubtful?