Reference for Avodah Zarah 47:20

ת"ש (שמות יח, יב) ויקח יתרו חתן משה עולה וזבחים לאלהים יתרו נמי קודם מתן תורה הוה הניחא למ"ד יתרו קודם מתן תורה הוה אלא למ"ד

Come and hear: “And Jethro, Moses’ father-in-law, took a burnt-offering and sacrifices for God” (Exodus 18:12). Jethro also occurred before the giving of the Torah This works according to the one who says that Jethro's [visit to Moses] came before the giving of the Torah, but according to the one who says that

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