Jerusalem Talmud Yevamot 13.13

משנה: גְּדוֹלָה וּקְטַנָּה בָּא הַיָּבָם עַל הַגְּדוֹלָה וְחָזַר וּבָא עַל הַקְּטַנָּה. אוֹ שֶׁבָּא אָחִיו עַל הַקְּטַנָּה לֹא פָסַל אֶת הַגְּדוֹלָה. בָּא הַיָּבָם עַל הַקְּטַנָּה וְחָזַר וּבָא עַל הַגְּדוֹלָה אוֹ שֶׁבָּא אָחִיו עַל הַגְּדוֹלָה פָּסַל אֶת הַקְּטַנָּה. רִבִּי לָעְזָר אוֹמֵר מְלַמְּדִין אֶת הַקְּטַנָּה שֶׁתְּמָאֵן בּוֹ.

MISHNAH: An adult wife and an underage one. If the levir had intercourse with the adult and then had intercourse with the underage one, or his brother had intercourse with her, the adult was not disabled. If the levir had intercourse with the underage widow and then had intercourse with the adult one, or his brother had intercourse with her, the underage one was disabled. Rebbi Eleazar says, one teaches the underage girl that she should repudiate him.

הלכה: גְּדוֹלָה וּקְטַנָּה. בָּא הַיָּבָם כול׳. אֲפִילוּ לֹא בָא עַל הַגְּדוֹלָה פּוֹסֵל אֶת הַקְּטַנָּה. שֶׁאִילּוּ לֹא בָא עַל הַגְּדוֹלָה וָמֵתָה הָיָה מוּתָּר בַּקְּטַנָּה. וְעַכְשָׁיו שֶׁבָּא עָלֶיהָ אֲפִילוּ מֵתָה פָּסַל אֶת הַקְּטַנָּה.

HALAKHAH: “An adult wife and an underage one” Even if he did not have intercourse with the adult one, the underage one is disabled. If he did not have intercourse with the adult woman and she died, he would have been permitted the underage one. But now that he did have intercourse with her, even if she died he had disabled the underage one.

רִבִּי לָעְזָר אָמַר מְלַמְּדִין אֶת הַקְּטַנָּה שֶׁתְּמָאֵן בּוֹ. לְשֶׁעָבַר. הָא כַּתְּחִילָּה לֹא. רִבִּי מָנָא אָמַר לָהּ סְתָם. רִבִּי יִצְחָק בְּרֵיה דְּרִבִּי חִיָיה כְּתוֹבָה בְשֵׁם דְּרִבִּי יוֹחָנָן. דְּרִבִּי מֵאִיר הִיא. דְּרִבִּי מֵאִיר אָמַר. אֵין חוֹלְצִין וְלֹא מְיַיבְּמִין אֶת הַקְּטַנָּה שֶׁמָּא תִימָּצֵא אַיְילוֹנִית.

“Rebbi Eleazar says, one teaches the underage girl that she should repudiate him.” After the fact. Therefore, not from the start! Rebbi Mana said it without attribution, Rebbi Isaac the son of Rebbi Ḥiyya the Scribe in the name of Rebbi Yoḥanan: This is Rebbi Meїr’s, since Rebbi Meїr said that one does not perform levirate or ḥalîṣah with an underage girl, since she might be found to be a she-ram.