Reference for Kiddushin 3:5
הַמְקַדֵּשׁ אֶת הָאִשָּׁה וְאָמַר, כְּסָבוּר הָיִיתִי שֶׁהִיא כֹהֶנֶת וַהֲרֵי הִיא לְוִיָּה, לְוִיָּה וַהֲרֵי הִיא כֹהֶנֶת, עֲנִיָּה וַהֲרֵי הִיא עֲשִׁירָה, עֲשִׁירָה וַהֲרֵי הִיא עֲנִיָּה, הֲרֵי זוֹ מְקֻדֶּשֶׁת, מִפְּנֵי שֶׁלֹּא הִטְעַתּוּ. הָאוֹמֵר לְאִשָּׁה, הֲרֵי אַתְּ מְקֻדֶּשֶׁת לִי לְאַחַר שֶׁאֶתְגַּיֵּר אוֹ לְאַחַר שֶׁתִּתְגַּיְּרִי, לְאַחַר שֶׁאֶשְׁתַּחְרֵר אוֹ לְאַחַר שֶׁתִּשְׁתַּחְרְרִי, לְאַחַר שֶׁיָּמוּת בַּעֲלֵךְ אוֹ לְאַחַר שֶׁתָּמוּת אֲחוֹתֵךְ, לְאַחַר שֶׁיַּחֲלֹץ לָךְ יְבָמֵךְ, אֵינָהּ מְקֻדֶּשֶׁת. וְכֵן הָאוֹמֵר לַחֲבֵרוֹ, אִם יָלְדָה אִשְׁתְּךָ נְקֵבָה הֲרֵי הִיא מְקֻדֶּשֶׁת לִי, אֵינָהּ מְקֻדֶּשֶׁת. אִם הָיְתָה אֵשֶׁת חֲבֵרוֹ מְעֻבֶּרֶת וְהֻכַּר עֻבָּרָהּ, דְּבָרָיו קַיָּמִין, וְאִם יָלְדָה נְקֵבָה, מְקֻדֶּשֶׁת:
If one betrothed a woman and said: "I thought she was the daughter of a Cohein, and she is the daughter of a Levite; the daughter of a Levite, and she is the daughter of a Cohein; poor, and she is rich; rich, and she is poor" — she is betrothed, for she did not deceive him. If one said to a woman: "You are betrothed to me after I become a proselyte," or: "after you become a proselyte"; "after I gain my freedom (from bondsmanship" or: "after you gain your freedom"; "after your husband dies" or: "after your sister (his wife) dies"; "after your yevamah gives you chalitzah" — she is not betrothed. Likewise, if one says to his friend: "If your wife gives birth to a girl, she is betrothed to me" — she is not betrothed. If his friend's wife were pregnant, and her fetus were recognizable, his words stand, and if she gives birth to a girl, she is betrothed. [Rambam writes that he should not live with her until he betroths her a second time. For "a man cannot bestow something which has not yet entered the world." They stated: "His words stand" only to impose a stringency upon her, that she be forbidden to wed others.]