Siman 49
Presented here for study, not as a practical ruling. The Shulchan Aruch rules by Sephardi custom, the Rema's glosses by Ashkenazi custom, and the Kitzur follows Ashkenazi custom. For a practical question, ask your rabbi.
א הַמְקַדֵּשׁ אַחַת מֵחָמֵשׁ נָשִׁים וְכָתַב לָהּ כְּתֻבָּה, וְאֵינוֹ יוֹדֵעַ אֵיזוֹ הִיא, וְכָל אַחַת מֵהֶן אוֹמֶרֶת: אֲנִי הִיא, אָסוּר בִּקְרוֹבוֹת כֻּלָּן וְנוֹתֵן גֵּט לְכָל אַחַת וְאַחַת וּמַנִּיחַ כְּתֻבָּה בֵּינֵיהֶם וּמִסְתַּלֵּק. וְאִם קִדֵּשׁ בְּבִיאָה, קָנְסוּ אוֹתוֹ חֲכָמִים שֶׁיִּתֵּן כְּתֻבָּה לְכָל אַחַת וְאַחַת:
1 If a man is mekadesh (that is, betroths) one of five women, and he writes and delivers to her a ketuba (that is, a marriage document guaranteeing a certain amount of money to the women should the husband die or divorce her), and he does not know which one [of the five women] he married, and each [woman] says, "I am the one," he is forbidden to marry the relatives of all of them [as if each one is the "true" wife] and he gives a get (that is, a bill of divorce) to each one of them and he gives the ketuba money (that is, money given to a divorcee by the husband) between all of them and leaves [i.e., he leaves it up to the women to decide who was the "true" wife and, therefore, who has rights to the ketuba money]. If he was mekadesh her through engaging in sexual relations, the Sages punished him and he must give the ketuba money to each of the women.
ב הַמְקַדֵּשׁ אִשָּׁה וְחָזַר בּוֹ מִיָּד, וְאָמַר שֶׁהַמָּעוֹת יִהְיוּ מַתָּנָה, אֲפִלּוּ תּוֹךְ כְּדֵי דִּבּוּר, אֵין חֲזָרָתוֹ כְּלוּם וּצְרִיכָה גֵּט:
2 Someone who marries a woman, and retracts immediately, and says that the money is a gift, even saying so in the same breath, his retraction is meaningless, and he thus requires a bill of divorce.
ג כָּל מִי שֶׁאֵינוֹ בָּקִי בְּטִיב גִּטִּין וְקִדּוּשִׁין לֹא יְהֵא לוֹ עֵסֶק עִמָּהֶם לְהוֹרוֹת בָּהֶם, שֶׁבְּקַל יָכוֹל לִטְעוֹת וְיַתִּיר אֶת הָעֶרְוָה וְגוֹרֵם לְהַרְבּוֹת מַמְזֵרִים בְּיִשְׂרָאֵל:
3 Anyone who is not an expert in the make-up of divorces and marriages should not deal with them to teach (about them, because it is easy to err and to permit an erva [that is, a forbidden woman] and cause an increase in mamzerim [that is, children born from illicit relationships] in Israel.