How big does a stain have to be before it renders a woman temei'ah?

An important note: this siman contains many details that affect one another. Until we finish the whole siman and have all the information in hand, do not draw conclusions about real situations that may arise. If a question comes up before we have finished, seek halachic guidance.

Practical halachah

A stain renders a woman temei'ah only if it is larger than a gris.

Hebrew speakers may be thrown by the term "gris," since in modern Hebrew גריסים are barley grains. The halachic gris is not a barley grain but a fava bean.

There is a machloket about its exact size:

Measuring in practice

American women have a gift here: the penny is exactly 19 mm.

In Israel no coin matches precisely:

Sometimes a stain is roughly circular and easy to compare to a coin. Usually it is not. A woman who is unsure whether a stain is larger or smaller than a gris should ask.

Note: a stain on a colored surface (see the article on stains on a colored surface), or on a surface that cannot receive tum'ah (see the article on location on the body), does not render a woman temei'ah even if it is larger than a gris. So the only cases in which a woman measures a stain are a stain on white clothing, on the skin, or on an object that can receive tum'ah.

Expanding the sources — the origin of the leniency

Masechet Niddah (58b) teaches that although the Sages decreed that a woman who finds a bloodstain becomes a niddah, if there is an alternative source to which the stain can be attributed, we say the blood came from that source and the woman is not a niddah.

One alternative source the Mishnah mentions is a louse.

In the time of Chazal lice were extremely common, on the body and in the bedding. Crushing a louse releases blood, leaving a bloodstain on whatever surface it was killed on.

The Mishnah says that a woman who killed a louse and afterwards found a bloodstain may attribute the stain to the louse and is not a niddah.

Rabbi Chanina ben Antigonus goes further: any woman may attribute a bloodstain to a louse, even with no knowledge of having killed one. Lice were so common that people would not notice they had crushed one. In the words of Chazal, "there is no bed that does not have on it several drops of the blood of lice."

How the Gemara defines the size

Rabbi Chanina then limits the leniency: not every size of stain can be attributed to a louse. Only a stain the size of a gris can be — the size you would expect from a crushed louse. He explains that a gris is the size of a fava bean.

The Gemara records a further machloket. When we say that as long as the stain is the size of a gris (and no more) the woman is not a niddah, do we mean a stain exactly the size of a gris, or must it be slightly smaller?

The rulings of the Rishonim and the Shulchan Aruch

Nearly all the Rishonim ruled like Rabbi Chanina ben Antigonus and Rav Chisda: even a woman who did not kill a louse may attribute a bloodstain to one, and the size that may be attributed is a gris.

The Rambam understood otherwise. While that is the law on a surface other than the woman's skin (clothing or furniture, say), a stain on the skin renders a woman temei'ah at any size.

The Shulchan Aruch rules with the majority of the Rishonim: if a woman found a bloodstain, even with no knowledge of having killed a louse, and it is the size of a gris or less, she is not a niddah. The Shulchan Aruch adds that the size of a gris also corresponds to the size of nine lentils.

Contemporary poskim — the measurements

But lice today don't produce that much blood

The question arises: can we still attribute gris-sized bloodstains to lice today, knowing that contemporary lice do not release blood in anything like the volume of a fava bean?

The Chatam Sofer explains that we can continue to rely on this leniency. It is a halachah the Sages enacted, and although the underlying reason no longer applies, the halachah stands.