Niddah 15b (טו:) — the Talmud in English

Rav Huna said:

They taught

that she retains a presumption of ritual purity, even when the time of her expected period has arrived,

only when she does not have a menstrual cycle determined by days

alone,

but she does have

a composite cycle

determined by days

and by jumping,

such that she sees blood only following a jump, and on fixed days.

Since the matter depends on an act

of jumping

with regard to

[her seeing blood], she retains her presumption of purity even if the time has arrived when, were she to jump, she would see blood, because we say:

Perhaps she will not jump and will not see blood

[since, as the change in her presumption is conditional upon her performing an act, we assume that the presumption continues and that the act of jumping that would change it will not take place].

But

if

she has a cycle determined by days

alone, and the day of her expected period has arrived,

she is forbidden to engage in intercourse

because she has lost her presumption of purity.

Rav Huna holds

that

“menstrual cycles are of Torah origin,”

and when the day of her expected period arrives, she has the status of a woman presumed impure by Torah law, as a matter of uncertainty, if she did not examine herself on that day. Therefore, even if she agrees to intercourse, her husband may not rely on her, assuming that she surely examined herself at the time of her expected period. Rather, he must ask her whether she in fact examined herself at that time and was found pure.

Rabba bar bar Ḥana said: Even if she has a cycle determined by days

and the time of her expected period has arrived,

she is permitted

to her husband who has come from a journey and does not know whether she examined herself at the time of her expected period, since she still retains her presumption of purity.

The Gemara explains:

Rabba bar bar Ḥana holds

that

“menstrual cycles are rabbinic in origin,”

as the Sages instituted that she examine herself on the day of her expected period, but they did not abrogate her presumption of purity.

Rav Shmuel said in the name of Rabbi Yoḥanan: With regard to a woman who has a menstrual cycle,

whose husband was away, and he returned seven days after the time of her expected period,

her husband

calculates the days of her menstrual cycle and engages in intercourse with her,

since he may rely on the assumption that she immersed herself after her seven days of menstruation, without asking her about it.

Rav Shmuel bar Yevai said to Rabbi Abba:

Does

Rabbi Yoḥanan

say that one may rely on the assumption that she immersed herself

even in the case of a young woman

[a minor]

who is reluctant to immerse herself

[because she is embarrassed to immerse unless her husband appeases her and encourages her to do so]?

He said to him,

Rabbi Abba:

Did Rabbi Yoḥanan really say, “She certainly saw blood,”

that one may rely on her immersion without asking her?

I can say that Rabbi Yoḥanan said

that, when the husband had been away and does not know whether she saw blood, since

“it is uncertain whether she saw blood or whether she did not see blood, and if you should say that she saw blood, perhaps she immersed herself” ,

the uncertainty concerning her immersion is sufficient to permit a woman whose having seen blood is itself uncertain!

Since Rabbi Yoḥanan’s ruling applies only when it is uncertain whether she saw blood, one may be lenient even in the case of a young woman who is embarrassed to immerse herself unless her husband appeases her. For in any event, even in the case of a young woman, there is uncertainty as to whether she immersed herself, and uncertainty concerning immersion is sufficient to permit her, since the bleeding as well is only an uncertainty .

But if she certainly saw blood—

one may not rely, as a matter of uncertainty, on the assumption that she immersed herself. For

“Who says that she immersed herself?”

And if so,

it is an uncertainty

regarding permissibility

and a certainty

regarding prohibition.

And an uncertainty

of permissibility

cannot remove

the status of

a certainty

of prohibition.

The Gemara asks:

Is that so?!

Can an uncertainty not override a certainty?

But it was taught in a beraita: A ḥaver

[who is presumed to separate terumot and tithes]

died, and left a storeroom full of produce,

and it is not known whether he separated terumot and tithes from it;

even if it is only one day old,

meaning that he brought it into the storeroom only that day—

it has the status of produce that has been tithed!

But here,

the produce was

certainly tevel

when it was brought into the storeroom, and now it is

uncertainly tithed and uncertainly untithed, and

nevertheless

an uncertainty comes

concerning the tithing

and removes

it from the status of a certainty

of tevel?!

The Gemara answers:

There—

it is a certainty and a certainty!

We are certain that the ḥaver tithed the produce before he died. And it is

in accordance with the statement of Rav Ḥanina Ḥoza’a,

as Rav Ḥanina Ḥoza’a said: It is presumed that a ḥaver does not allow something that is not properly prepared to leave his possession!

And if you prefer, say: It is an uncertainty and an uncertainty

[that is, even if the presumption concerning the ḥaver is not entirely conclusive, one may rely upon it, since the presumption that the produce is tevel is also not entirely conclusive]. It is possible that the produce is not tevel,

in accordance with the statement of Oshaya,

and the uncertainty whether he tithed it is sufficient to permit produce that is possibly tevel.

As Rabbi Oshaya said: A person may employ a stratagem with his produce

in order to exempt it from tithing by

bringing it into his house in its chaff

. Produce becomes prohibited as tevel only if its final processing was completed in the field and it was subsequently brought into the house. But if it was brought into the house before its final processing, it does not become prohibited as tevel, even if its processing is completed in the house.

One who brings produce into the house while it is still in its chaff, before its processing is complete, and completes its processing in the house, is employing a stratagem to exempt it from tithing. However, even though by Torah law produce brought into the house in its chaff does not become prohibited, it is prohibited by rabbinic law [the Sages prohibited regular eating of tevel even before its processing is complete]. Therefore, the stratagem is effective only

so that

his animal may eat it!

The eating of an animal, even in large quantities, is considered an incidental eating.

And still

it is difficult: Do we say

that a doubt does not displace certainty?

But it was taught in a beraita: There was an incident involving the maidservant of an olive presser [

olive presser ]

one, in Rimon [

a place name ],

who cast a stillborn fetus into a pit, and a kohen came and peered into it

in the pit,

to determine whether it was male

the stillborn fetus

or female,

with the practical difference being the number of days of ritual impurity and purity.

And the incident

involving that kohen

was brought before the Sages, and they declared him pure [

because he had not formed an ohel over the stillborn fetus when he peered into the pit ],

because a weasel and a ferret are commonly found there

and had dragged it from the pit.

But here,

in the case of the stillborn fetus that was in the pit,

it is certain that she cast

the maidservant

a stillborn fetus

into the pit, and it is uncertain whether it was dragged

by the weasel and the ferret,

or whether it was not dragged, and

nevertheless

a doubt comes

of dragging

and displaces

certainty

of a stillborn fetus?!