Yevamot 102A

גר דן את חבירו דבר תורה, שנאמר: ״שום תשים עליך מלך אשר יבחר ה׳ אלהיך בו מקרב אחיך תשים עליך מלך״. ״עליך״ הוא דבעינן ״מקרב אחיך״, אבל גר דן את חבירו גר.

By Torah law a convert may judge his fellow convert, as it is stated: “You should set a king over you, whom YHWH your God should choose; one from among your brothers you should set king over you” (Deuteronomy 17:15). The Talmud deduces from the terminology of the phrase “over you,” i.e., when presiding over Jews by birth either as a king, a judge, or any other official, that from here it is where we require that the official must be: “From among your brothers,” meaning a Jew by birth. However, a convert may judge his fellow convert, as the requirement of “one from among your brothers” doesn’t apply when presiding over fellow converts.

ואם היתה אמו מישראל ⁠— דן אפילו ישראל. ולענין חליצה עד שיהא אביו ואמו מישראל, שנאמר: ״ונקרא שמו בישראל״.

And if the convert’s mother was from Israel, he may even preside as a judge in a court to adjudicate legal matters involving a native-born Jew. But with regard to ḥalitza, he may not act as a judge unless both his father and his mother were from Israel from birth, as it is stated with regard to ḥalitza: “And his name should be called in Israel: The house of he who had his shoe removed” (Deuteronomy 25:10), implying that he must be born as a member of the Jewish people from both of his parents.

אמר רבה אמר רב כהנא אמר רב: אם יבא אליהו ויאמר: ״חולצין במנעל״⁠ — שומעין לו. ״אין חולצין בסנדל״⁠ — אין שומעין לו, שכבר נהגו העם בסנדל.

§ Rabba said that Rav Kahana said that Rav said: If Elijah the Prophet should come and say: One may perform ḥalitza using a soft leather shoe, the Rabbis would listen to him. But if he says: One may not perform ḥalitza using a hard leather sandal, they would not listen to him, for the people already have established the practice of performing ḥalitza using a sandal.