Temurah 21A

עצמו ⁠— לא! הכא במאי עסקינן? כגון שילדה נקבה, ועד סוף העולם לא אוליד חד זכר?! אמר ליה: משנינא [לך] שינויי דחיקי בבלאי, כגון שילדה נקבות עד סוף העולם.

but the offspring itself is not sacrificed as a burnt offering. R' Avin bar Kahana responds: What are we dealing with here? It is a case where the female designated as a guilt offering or as the substitute of a guilt offering gave birth to a female, which cannot itself be offered as a guilt offering. R' Avin bar Ḥiyya asks: This is problematic, as the Mishnah states that the same is true with regard to the offspring of its offspring until the end of time. But could the Mishnah be referring to a case where until the end of time not even one male was born? R' Avin bar Kahana said to him in response: I answer forced answers, in the manner of the Babylonians, and say that the Mishnah is referring to a case where it gave birth to females, and those females also gave birth to females, until the end of time.

מתני׳ תמורת הבכור והמעשר, ולדן ולד ולדן עד סוף העולם ⁠— הרי אלו כבכור וכמעשר, ויאכלו במומן לבעלים.

Mishnah: With regard to the substitute of a firstborn offering and the substitute of an animal tithe offering, and the offspring of those substitutes and the offspring of their offspring until the end of time, the halakhic status of these animals is like that of a firstborn offering and like that of an animal tithe offering in that they must be treated with sanctity: They graze until they become blemished, and at that point they may be eaten in their blemished state, the substitute of the firstborn by the priests and the substitute of the animal tithe by their owners. They are not sacrificed upon the altar like the original firstborn and animal tithe offerings.