That he not bring back his ex-wife from when she has married: That we have been prevented from bringing back a woman after we have divorced her and she has married another. And [that is] specifically when she married or became engaged (with formal erusin); but if she was promiscuous after he divorced her, it is permissible to bring her back. And about this is it stated (Deuteronomy 24:4), “The first husband who divorced her may not take her to wife again.” And this is speaking about after she married another — as it stated first, “and becomes the wife of another man.” As if it is before she married [another], it is permissible to bring her back; and it is also appropriate to do so, if she is not an evildoer.
It is from the roots of this commandment [that it is] in order to distance all matters of licentiousness and anything similar to it. And I have already written in the Order of Acharei Mot (Sefer HaChinukh 188) and concerning the negative commandment of “Do not commit adultery” in the Order of Vayishma Yitro (Sefer HaChinukh 35) [about] the multitude of harm that is [involved] in licentiousness, and the matter is known. And like the matter of licentiousness is it for a woman to go out from one [man], and have relations with others, and afterwards to come back to the first.
And this prohibition is practiced in every place and at all times by males — as the warning to not bring them back comes to them. And nonetheless, women are also included in the prohibition, even though the main negative commandment is upon men. And Ramban, may his memory be blessed, (15 in the negative commandments according to the opinion of Ramban, in Sefer HaMitzvot) enumerates two negative commandments in this: One is not to bring back an ex-wife after she has married; and the [other] is that the husband should not have sexual relations with his wife after she has been promiscuous while she is still [married] to him.
שֶׁלֹּא יַחְזִיר גְּרוּשָׁתוֹ מִשֶּׁנִּשֵּׂאת – שֶׁנִּמְנַעְנוּ מִלְּהַחְזִיר הָאִשָּׁה אַחַר שֶׁגֵּרַשְׁנוּהָ וְנִשֵּׂאת לְאַחֵר, וְדַוְקָא נִשֵּׂאת אוֹ נִתְאָרְסָה, אֲבָל זָנְתָה אַחַר שֶׁגֵּרְשָׁהּ מֻתָּר לְהַחְזִירָהּ, וְעַל זֶה נֶאֱמַר (דברים כד ד) לֹא יוּכַל בַּעְלָהּ הָרִאשׁוֹן אֲשֶׁר שִׁלְּחָהּ לָשׁוּב לְקַחְתָּהּ, וְזֶה יְדַבֵּר אַחַר שֶׁנִּשֵּׂאת לְאַחֵר, כְּמוֹ שֶׁאָמַר תְּחִלָּה וְהָלְכָה וְהָיְתָה לְאִישׁ אַחֵר, דְּאִלּוּ קֹדֶם שֶׁתִּנָּשֵׂא מֻתָּר לְהַחְזִירָהּ, וְגַם רָאוּי לַעֲשׂוֹת כֵּן אִם אֵינָהּ רְשָׁעָה.
That he not bring back his ex-wife from when she has married: That we have been prevented from bringing back a woman after we have divorced her and she has married another. And [that is] specifically when she married or became engaged (with formal erusin); but if she was promiscuous after he divorced her, it is permissible to bring her back. And about this is it stated (Deuteronomy 24:4), “The first husband who divorced her may not take her to wife again.” And this is speaking about after she married another — as it stated first, “and becomes the wife of another man.” As if it is before she married [another], it is permissible to bring her back; and it is also appropriate to do so, if she is not an evildoer.
מִשָּׁרְשֵׁי הַמִּצְוָה. כְּדֵי לְהַרְחִיק כָּל עִנְיַן הַזִּמָּה וְכָל הַדּוֹמֶה לוֹ, וּכְבָר כָּתַבְתִּי בְּסֵדֶר אַחֲרֵי מוֹת (מצוה קפח) וּבְלָאו דְּלֹא תִּנְאָף בְּסֵדֶר וַיִּשְׁמַע יִתְרוֹ (מצוה לה), רִבּוּי הַנְּזָקִים שֶׁהֵן בַּזִּמָּה, וְיָדוּעַ הַדָּבָר, וּכְעֵין זִמָּה הִיא לִהְיוֹת אִשָּׁה יוֹצֵאת מִן הָאֶחָד וּמְשַׁמֶּשֶׁת לַאֲחֵרִים וְאַחַר כָּךְ לָשׁוּב אֶל הָרִאשׁוֹן.
It is from the roots of this commandment [that it is] in order to distance all matters of licentiousness and anything similar to it. And I have already written in the Order of Acharei Mot (Sefer HaChinukh 188) and concerning the negative commandment of “Do not commit adultery” in the Order of Vayishma Yitro (Sefer HaChinukh 35) [about] the multitude of harm that is [involved] in licentiousness, and the matter is known. And like the matter of licentiousness is it for a woman to go out from one [man], and have relations with others, and afterwards to come back to the first.
דִּינֵי הַמִּצְוָה. בִּמְקוֹמוֹת מִיְּבָמוֹת [א"ה סי' י].
The laws of this commandment are in [various] places [in] Yevamot. (See Tur, Even HaEzer 10.)
וְנוֹהֵג אִסּוּר זֶה בְּכָל מָקוֹם וּבְכָל זְמַן בִּזְכָרִים, שֶׁעֲלֵיהֶן בָּאָה הָאַזְהָרָה שֶׁלֹּא לְהַחְזִירָן, וּמִכָּל מָקוֹם גַּם הַנָּשִׁים בִּכְלַל הָאִסּוּר, אַף עַל פִּי שֶׁעִקַּר הַלָּאו לָאֲנָשִׁים. וְהָרַמְבַּ"ן זִכְרוֹנוֹ לִבְרָכָה (בספהמ"צ לאוין לדעת הרמב"ן ט"ו) יִמְנֶה בָּזֶה הַכָּתוּב שְׁנֵי לָאוִין, הָאֶחָד שֶׁלֹּא לְהַחְזִיר הַגְּרוּשָׁה אַחַר שֶׁנִּשֵּׂאת, וְהָאֶחָד שֶׁלֹּא יָבוֹא הַבַּעַל עַל אִשְׁתּוֹ אַחַר שֶׁזָּנְתָה בְּעוֹדָהּ תַּחְתָּיו.
And this prohibition is practiced in every place and at all times by males — as the warning to not bring them back comes to them. And nonetheless, women are also included in the prohibition, even though the main negative commandment is upon men. And Ramban, may his memory be blessed, (15 in the negative commandments according to the opinion of Ramban, in Sefer HaMitzvot) enumerates two negative commandments in this: One is not to bring back an ex-wife after she has married; and the [other] is that the husband should not have sexual relations with his wife after she has been promiscuous while she is still [married] to him.