Bekhorot 21a — the Talmud in English

Shall we say that the first tanna

holds that

an animal that has a discharge does not return and give birth within its year.]] That is to say, even if it had a discharge in this year, it again does not return and give birth until a year has elapsed from its discharge; and all the more so this one, which gave birth in this year, does not return and give birth until a year has elapsed from the previous birth. And therefore it is impossible to combine daughter after daughter for the animal tithe, because they were not born in one year.

That is, even if it discharged a nonviable fetus during this year, it does not become pregnant again and give birth until a full year has passed from that discharge. All the more so, an animal that gave birth during this year does not become pregnant again and give birth until a full year has passed from its previous birth. Therefore, it is impossible to combine successive daughters for the animal tithe, because they were not born within one year.

And we reject this:

even if you should say that an animal that has a discharge returns and gives birth within its year,

but

one that gives birth

to a complete offspring

certainly does not return and give birth within its year,

and it is impossible for an animal to give birth to daughter after daughter within one year.

The Gemara adds to explain the continuation of the beraita:

Rabbi Shimon said: I saw a young goat

that was tithed within its year:

And the Gemara discusses:

What difference is there between the first tanna and Rabbi Shimon?

And the Gemara explains that they disputed a case in which the daughters had discharges on the last day of the sixth month from their birth. And their dispute is that, according to the first tanna, you find that the daughters and the daughters’ daughters are tithed only if the daughters gave birth on the day the year from their birth ended, whereas Rabbi Shimon holds that sometimes you find that the daughters and the daughters’ daughters are tithed even “within its year,” that is, even within—and not at the end of—that same year in which the mother gave birth to the first three daughters. And the Gemara explains the foundation of their dispute in several ways:

The first manner:

The difference between them

between the first tanna and Rabbi Shimon—is

that of Zeiri.

For Zeiri said: A discharge is not less than thirty days,

meaning that it does not accept a male until thirty days from the time that it had the discharge:

The first tanna holds like Zeiri,

and you must count from the day of their discharge, which was on the day the sixth month from their birth ended, another full thirty days. Only on the following day, at the end of the seventh month from the time they were born, do they accept a male; and again you must allow five full months for their gestation, and they give birth on the following day, that is, on the day the year from their birth ends.

But

if

Rabbi Shimon does not hold like Zeiri,

they need not wait thirty days from their discharge until they accept a male. It follows that even if they had discharges on the day six months from their birth ended, they can give birth in the last month of their year, and not specifically on the day their year from birth ends.

The second manner:

And if you wish, say

to explain the foundation of their dispute:

everyone holds like Zeiri,

that she does not accept a male until thirty days from her discharge,

and here they dispute concerning one who gives birth by partial periods:

The first tanna holds: she does not give birth by partial periods,

and she does not give birth until the day after the completion of five months of gestation.

And Rabbi Shimon holds: she gives birth by partial periods,

and she can give birth during the fifth month of her gestation, and not specifically on the day her year from birth ends.

The third manner:

And if you wish, say: everyone holds that she does not give birth by partial periods, and here they dispute concerning [the principle that] a part of the day is like the whole day,

whether part of the last day of the thirty days from her discharge, and part of the last day of the five months of her gestation, are considered a full day;

according to the first tanna, we do not say “

a part of the day is like the whole day,”

and she requires thirty full days from her discharge, and only on the following day does she accept a male; and likewise she requires five full months, so that she gives birth on the following day. It follows that she will not give birth until the last day of the year of her birth.

According to Rabbi Shimon, we say “

a part of the day is like the whole day,”

and it follows that she gives birth one or two days before the end of the year of their birth.

The fourth manner:

And if you wish, say: everyone says that a part of the day is like the whole day.

And here they dispute concerning one lacking time,

before the eighth day from birth, when it is not fit for sacrifice, as it is written: “And from the eighth day onward it shall be accepted as an offering made by fire to the Lord”—whether it

enters the pen to be tithed, they dispute:

The first tanna holds:

one lacking time

does not enter the pen to be tithed.

And Rabbi Shimon holds:

one lacking time

enters the pen to be tithed.

And therefore Rabbi Shimon said that they are tithed within their year, meaning that it is possible to tithe them within the year in which they were born, on the very day of their birth, when they were born before the end of the day. But according to the first tanna, they are tithed for the following year.