Bekhorot 17b (יז:) — the Talmud in English

and he is obligated —

the second one, whom the Israelite took—

in the gifts

of the priesthood [the foreleg, the cheeks, and the maw]. But the animal that the kohen took is not subject to the gifts, since a kohen is not obligated in the gifts.

And Rabbi Yosei exempts

even the Israelite from the gifts of the priesthood; their rationale will be explained in the Gemara.

And if

one of them dies:

Rabbi Tarfon says: They divide it.

Rabbi Akiva says:

It shall remain in the possession of the Israelite [and he shall let it graze until it develops a disqualifying blemish, and he may eat it because of its blemish], because

the burden of proof rests upon the one who seeks to extract property from his fellow;

therefore, the kohen who seeks to extract it must bring proof. The Gemara will explain in what manner they disagree and the rationales for their opinions.

And if she gives birth to

a male and a female

and their two heads emerge simultaneously, since it is impossible to determine precisely, it is possible that the female emerged first, and

the kohen has nothing here

because the burden of proof rests upon the one who seeks to extract property from his fellow.

Gemara:

The scholars of the school of Rabbi Yannai say:

We have heard from Rabbi Yosei HaGelili

in our Mishna

that he says: Precise determination is possible by the hand of Heaven.

That is, even something that was not intentionally made precise and exact, such as something brought about by Heaven—as in our Mishna, with the birth of two males—or by a person without the intention of making it precise: once it appears to us to be exact and precise, we say that it is indeed exact and precise—

and all the more so

that precise determination is possible

by human hands,

meaning when something was initially done with the intention of making it precise and exact. It is obvious according to Rabbi Yosei’s view that if it appears to us to be exact and precise, we assume that it is indeed exact and precise, since that was the intention.

And as for the Rabbis,

we hear them in our Mishna holding that:

by the hand of Heaven—

as in the birth of two males, where there was no intention of making it precise—

precise determination is impossible.

However, according to their view, the question arises: If it is

by human hands,

where one intended to make it precise and exact and it was found to be exact and precise,

what

is the law? Do we assume that it is indeed exact and precise?

Come and hear:

A scarlet thread

[that was] dyed red

encircled

the altar

in the middle,

in order

to distinguish between the upper bloods

that is, blood whose law is that it must be sprinkled above the midpoint of the altar,

and between the lower bloods,

that is, blood whose law is that it must be sprinkled from the midpoint of the altar and below. That thread was placed at the midpoint of the altar so that the kohen would know where to sprinkle.

And if you say that precise determination is impossible

even

by human hands,

then, although when the thread was placed they intended to make it precise and exact at the midpoint of the altar, we assume that they did not make it precise and exact,

and

it follows that

at times he gives

the kohen gives blood

of the upper offerings below,

the midpoint of the altar, because although he sprinkles above the thread, perhaps the thread is not at the midpoint but below it,

and

at times the kohen gives blood

of the lower offerings above,

because perhaps the thread is above the midpoint. Rather, it must be that when they intended to make it precise and exact, it is indeed so, even according to the Rabbis.

And we reject this:

The thread is made somewhat wider.

That is, they do not place a thin thread but a wide one, so that even if it is not positioned precisely, everything above the thread is certainly the upper half and everything below it is the lower half.

Come and hear from the measurements of the vessels

of the Tabernacle and the Temple

and from the measurement of the altar,

for if you say that precise determination is impossible even when one intends to make a measurement exact, the vessels and the altar would not be valid, since all their measurements have precise dimensions.

And we reject this:

There it is different, as the Merciful One said

“make”

[make this measurement or that one],

and whatever way you are able to make it is acceptable to Him

[and it is valid however you make it]. Even if it is not absolutely precise, but only appears so to us, it is valid.

Rav Ketina said: Come and hear:

An impure earthenware oven that was broken and divided: the part containing the majority of the vessel remains impure, whereas the other part is pure.

If they divided it

an impure earthenware oven

into two, and they are

[the two parts]

equal, both are impure, because precise determination is impossible.

One of them contains the majority of the vessel and therefore remains impure, but since we do not know which one it is, both are impure. It is thus evident that even when one intends to make the division precise and exact, we assume that it is not exact and precise; otherwise, we should have declared both parts pure, since neither contains the majority of the vessel.

Rav Kahana said

[and rejected this]:

An earthenware vessel is different, since it has indentations,

for it is not divided equally. When it is broken, protrusions remain in it, forming an indentation here and in many other places, and therefore it is impossible to assess those protrusions precisely.

Come and hear:

If a slain person is found and it is not known who killed him, the court measures toward the city nearest to the corpse, and that city brings a heifer, whose neck is broken in a stream, in order to atone for the city.

The slain person was found

the murdered person

exactly between two towns

[at an equal distance from the two towns on either side of the place where he was found], then

both bring two heifers

whose necks are broken—

the words of Rabbi Eliezer.

But

what is the reason

for Rabbi Eliezer? Is it

not because he holds

like the Rabbis, that precise determination is impossible, but nevertheless,

by human hands—

that is, when the court measures—

precise determination is possible, and

when the Torah says [Deuteronomy 21:3]: “And it shall be, the city

nearest

to the corpse, and the elders of that city shall take a heifer,” it means:

even

if there are two cities

near

the corpse, both bring a heifer? This shows that one who holds that precise determination is impossible concedes that by human hands it is possible.

And we reject this: No—

not as you explained Rabbi Eliezer’s position, that he holds like the Rabbis of our Mishna, who say that precise determination is impossible. Rather:

not as you explained Rabbi Eliezer’s view, that he holds like the Sages of our Mishna that exact simultaneity is impossible. Rather: