Yoma 64A

רבא אמר: כגון שהיה לו חולה בתוך ביתו, ושחט אמו ביום הכפורים.

The Talmud presents another explanation as to why a verse is needed to indicate that the scapegoat may not be lacking time. Rava said: It is referring to a case where the one who sold the two goats had a critically ill person in his household, and he slaughtered the mother of the scapegoat in order to save the ill person’s life on Yom Kippur. Although the scapegoat is more than 8 days old, it is considered lacking time because it is prohibited to slaughter a mother animal and its offspring on the same day.

וכי האי גוונא מי אסיר? ״לא תשחטו״ אמר רחמנא, והא לאו שחיטה היא! הא אמרי במערבא דחייתו לצוק זו היא שחיטתו.

The Talmud asks: Is it prohibited in a case like this? God stated in the Torah: “And whether it be a cow or ewe, you should not slaughter it and its young on one day” (Leviticus 22:28), and this act of pushing the scapegoat off the cliff is not a ritual slaughter. Consequently, the prohibition against slaughtering a mother animal and its offspring should not apply. The Talmud answers: They say in the West, i.e., Eretz Yisrael, that pushing it off the cliff, which is the manner in which the scapegoat is supposed to be killed, is considered its slaughter.

אם של שם מת, זה שעלה עליו וכו׳.

§ It was taught in the Mishnah that if one of the goats dies after the lottery, a second pair of goats is sought and new lots are drawn. After that lottery, the priest utters a stipulation: If the one to be sacrificed to God died, that goat upon which the lot for God was drawn should stand in its stead; and if the one to be sent to Azazel died, that goat upon which the lot for Azazel was drawn should stand in its stead. The second, superfluous goat should graze until it becomes blemished, at which point it will be sold and the money received in its sale will go to the purchase of a public gift-offering. The Talmud discusses which goat is set to pasture: The one that remains from the first lottery or the one that remains from the second lottery?