א אָמַר לָהּ: הֲרֵי אַתְּ מֻתֶּרֶת לְכָל אָדָם, חוּץ מִפְּלוֹנִי, אוֹ אֶלָּא לִפְלוֹנִי, אֵינוֹ גֵּט. כֵּיצַד יַעֲשֶׂה, יִטְּלֶנּוּ מִמֶּנָּה וְיַחֲזֹר וְיִתְּנֶנּוּ וְיֹאמַר: הֲרֵי אַתְּ מֻתֶּרֶת לְכָל אָדָם. אֲבָל אִם אָמַר: עַל מְנָת, הֲרֵי הוּא כִּשְׁאָר תְּנָאֵי הַגֵּט, בֵּין אָמַר לָהּ: עַל מְנָת שֶׁלֹּא תִּנָּשֵׂא לוֹ, אוֹ עַל מְנָת שֶׁלֹּא תִּבָּעֲלִי לוֹ, אוֹ עַל מְנָת שֶׁלֹּא תִּהְיִי לוֹ. וְיֵשׁ מַחֲמִירִין אֲפִלּוּ בְּאוֹמֵר עַל מְנָת (הָרַ"ן בְּשֵׁם י"א וְהָרַשְׁבָּ"א בְּשֵׁם הָרַמְבַּ"ן), וְיֵשׁ לְהַחֲמִיר לְכַתְּחִלָּה. וְאִם חוֹשְׁדָּהּ מֵאָדָם, יֹאמַר לְבֵית דִּין וְהֵם יִמְחוּ בְּיָדָם שֶׁלֹּא יִשְּׂאוּ זֶה אֶת זֶה (מָרְדְּכַי רֵישׁ הַמְגָרֵשׁ):
1 [If] he says to her, "Behold you are permitted to any man except for so-and-so," or "beside so-and-so", it is not a get [bill of divorce]. What should he do? He should take it from her, and give it to her again and say, "Behold you are permitted to any man." But if he says, "On condition..." ["al menat"] that is like any condition on a get [which is fine], whether he says, "On condition you do not marry him," or "on condition you not not become his spouse," or "on condition you do not become his." Rema: Some are stringent even when he says "al menat" (Ran in the name of Y"A, Rashba in the name of the Ramban_, and some are stringent [only] in an ideal case. And if she is suspected of cheating with a certain man, he should tell Bet Din and they will prevent them from marrying each other (Mordechai beginning of Hamegaresh).