Yoma 28b
יומא כ״ח ב — ד"ה אָמַר רַב יוֹסֵף
Yoma 28b:4
A baraita teaches that while the entire eighth day is suitable for circumcision according to the verse in Leviticus, the diligent perform the mitzva early in the morning, as evidenced by Abraham's early rising to fulfill the binding of Isaac, demonstrating that halakha may be derived from Abraham's conduct.
אָמַר רַב יוֹסֵף: אֲנַן מֵאַבְרָהָם נֵיקוּם וְנִיגְמַר?! אָמַר רָבָא: תְּנָא גָּמַר מֵאַבְרָהָם וַאֲנַן לָא גָּמְרִינַן מִינֵּיהּ?! דְּתַנְיָא: ״וּבַיּוֹם הַשְּׁמִינִי יִמּוֹל בְּשַׂר עׇרְלָתוֹ״, מְלַמֵּד שֶׁכׇּל הַיּוֹם כָּשֵׁר לְמִילָה, אֶלָּא שֶׁהַזְּרִיזִין מַקְדִּימִין לְמִצְוֹת, שֶׁנֶּאֱמַר: ״וַיַּשְׁכֵּם אַבְרָהָם בַּבֹּקֶר וַיַּחֲבוֹשׁ וְגוֹ׳״.
Rav Yosef said: And will we arise and derive a halakha from Abraham? Didn’t Abraham live before the Torah was given to the Jewish people, and therefore halakhot cannot be derived from his conduct? Rava said: The tanna derived a halakha from Abraham’s conduct, and we do not derive a halakha from his conduct? As it was taught in a baraita with regard to the verse: “And on the eighth day the flesh of his foreskin shall be circumcised” (Leviticus 12:3), this verse teaches that the entire day is suitable for performance of the mitzva of circumcision. However, the vigilant are early in their performance of mitzvot and circumcise in the morning, as it is stated with regard to the binding of Isaac: “And Abraham arose early in the morning and saddled his donkey” (Genesis 22:3). He awakened early to fulfill the mitzva without delay. Apparently, halakha is derived from the conduct of Abraham.