R. Yitzchak bar Bisna lost the keys to the Beis Medrash in a Reshus ha'Rabim on Shabbos.

R. Pedas: Get children to play there. If they find the keys, they will bring them.

He holds that if a child is eating forbidden food (or doing any other Isur), Beis Din need not stop him.

Support (Beraisa): A man should not tell a child 'bring to me a key [through Reshus ha'Rabim]' or 'bring to me a stamp' but he may allow the child to uproot or throw things.

Rejection (Abaye): The case is, he uproots from a flowerpot without holes (what grows inside is not considered attached to the ground) or throws in a Karmelis (these are forbidden only mid'Rabanan).

Question (Mishnah): If a Nochri comes to extinguish a fire, we do not tell him 'extinguish' or 'don't extinguish', since we are not commanded that he rest;

If a child comes to extinguish, we tell him 'don't extinguish', since we are commanded that he rest on Shabbos.

Answer (R. Yochanan): It is forbidden when the child does so to please his father.

Question: If so, similarly the Nochri does so to please the Yisrael. This is forbidden!

Answer: A Nochri acts in his own interest.

Support (Beraisa): If the son of a Chaver (one trustworthy about Ma'aser) often goes to his mother's father's house (who is not trustworthy), we are not concerned lest they feed him Tevel. If the father finds food in his son's hand, he is not responsible.

Rejection (R. Yochanan): This is no support. We are more lenient about Demai (doubtfully tithed produce).

Inference: If it were definitely Tevel, he would need to Ma'aser it.

Contradiction: Above, R. Yochanan answered 'he acts on his father's volition' (but we need not stop minors who transgress for their own benefit)!

Answer: R. Yochanan is in doubt what is the Halachah. He rejects the proofs for both opinions.

Support (Beraisa): If the son of a Kohen Chaver (who is reliable regarding Taharah) often goes to the house of his mother's father, an ignoramus Kohen, we are not concerned lest they feed him Tamei Terumah. If the father finds food in his hand, he is not responsible.

Rejection: This is no support. The Beraisa discusses Terumah mid'Rabanan.

Support (Beraisa): A child may nurse from a Nochris or a Tamei animal. We are not concerned that he suckles something detestable and forbidden;

One may not feed to a child Neveilah, Treifah, Tamei rodents or vermin;

The child may nurse from them even on Shabbos. An adult may not;

Aba Sha'ul says, we used to nurse from Tahor animals on Yom Tov.

Conclusion: The Beraisa says that we are not concerned that he suckles Isur!

Rejection: It is permitted because the child is in danger if he does not nurse.

Question: If so, it should be permitted even for an adult!

Answer: An adult is forbidden until we assess that he is in danger.

Question: A child should also need an assessment!

Answer (Rav Huna brei d'Rav Yehoshua): We assume that a child is in danger if he lacks milk.

(Beraisa - Aba Sha'ul): We used to nurse from Tahor animals on Yom Tov.

Question: What is the case?

If there is a danger, it should be permitted even on Shabbos!

If there is no danger, it should be forbidden even on Yom Tov!

Answer: The case is, they were in pain. He holds that nursing is Mefarek (extracting) in an unskillful manner, which is forbidden only mid'Rabanan.

On Shabbos one (who is Mefarek normally) is liable to stoning, therefore Chachamim decreed (against unskillful Mefarek, e.g. nursing, even though he is in pain);

Skilled Melachah on Yom Tov is only a Lav, so they did not decree to forbid one in pain.

Question (Beraisa): "Lo Tochlum (do not eat Sheratzim)" - we read this 'Lo Ta'achilum (do not feed them)', to warn adults about minors.

Suggestion: One must tell minors not to eat them!

Answer: No, this forbids giving them to minors to eat.

Question (Beraisa): "Every soul among you will not eat blood" warns adults about minors.

Suggestion: One must tell minors not to eat it!

Answer: No, this forbids giving it to minors to eat.

Question (Beraisa): It says "Emor" and "v'Omarta" (before the Lav for Kohanim to become Tamei), to warn adults about minors.

Suggestion: One must tell minors not to become Tamei!

Answer: No, this forbids making them Tamei.

All three verses are needed;

Had the Torah taught only about Sheratzim, one might have thought that this is because the Isur applies to any amount (if it is a full creature - Tosfos), but adults may feed blood to minors, for the Shi'ur (to be liable) for blood is a Revi'is;

Had the Torah taught only regarding blood, one might have thought that this is because there is Kares for eating blood; but adults may feed Sheratzim to minors.

Had the Torah taught only these two, one might have thought that this is because the Isur applies to everyone; but since Tum'ah applies only to Kohanim, adults may make minors Tamei.

Had the Torah taught only regarding Tum'ah, one might have thought this applies only there, since the Torah gave extra laws to Kohanim; but adults may give to minors Isurim that apply to everyone.

Question (Mishnah): If two brothers, one deaf and one Pike'ach, were married to two sisters Pikchos, and the Cheresh died, his wife is exempt from Chalitzah and Yibum, due to Achos Ishto;

If the Pike'ach died, the Cheresh must divorce his wife, and the Yevamah is forbidden forever.

Why must he divorce her? If we need not stop a minor from eating forbidden food, we need not stop a Cheresh from having forbidden Bi'ah!

Answer: He must divorce her because she is forbidden to him, and she is a Pikachas.

Question (Mishnah): If two brothers Pikchim were married to two sisters, a Chereshes and a Pikachas, and the Chereshes' husband died, she is exempt from Chalitzah and Yibum, due to Achos Ishto;

If the Pikachas' husband died, the Yavam must divorce his wife, and the Yevamah does Chalitzah.

Why must he divorce her? If we need not stop a minor from eating forbidden food, we need not stop a Chereshes from having forbidden Bi'ah!

Answer: He must divorce her, because he is forbidden to her, and he is a Pike'ach.

Question (Mishnah): If a Cheresh was married to a Chereshes, and his Pike'ach brother was married to her Pikachas sister, and the Cheresh died, his wife is exempt from Chalitzah and Yibum, due to Achos Ishto;

If the Pike'ach died, the Cheresh must divorce his wife, and the Yevamah is forbidden forever

Here, why must he divorce her? They are both Chershim!

Answer (Rav Shemayah): This is a decree lest people (who do not realize that they may stay married because they are exempt from Mitzvos) will think that their marriage dispels Zikah, and permit the Tzarah to marry a stranger.

(Mishnah): A woman went with her husband overseas. They were at peace, and there was peace in the world. If she returned and said that her husband died, she may remarry, or do Yibum if he had no children;

If she was at peace with her husband, but there was war in the world, or she was quarreling with her husband and there was peace in the world, she is not believed to say that he died;

R. Yehudah says, she is believed only if she returns crying and her clothes are torn;

Chachamim: Whether or not she is crying and has torn clothes, she is believed.

(Gemara): It says 'they were at peace' to exclude when they were quarreling. It says 'there was peace in the world' to exclude when there was war.

Question (Rava): Why is she not believed when there is war in the world?

Answer (Rava): She will testify based on estimation;

She thinks that everyone is getting killed. Will he really be saved?!

Question: Since she is at peace with him, she will wait until she sees that he died!

Answer: Sometimes he is hit with an arrow or spear, and she is sure that he will die;

She doesn't know that such wounds can be bandaged, and he can live.

(Rava): Famine is not like war. She would not testify from estimation.

Retraction (Rava): Famine is like war.

A woman came before Rava; she said that her husband died from hunger.

Rava: You were wise to leave in time to save yourself! Of course, he couldn't survive on the drop of flour remaining.

The woman: I see, you also know that people cannot survive in such circumstances!

Retraction (Rava): Famine is worse than war!

In wartime, if she says that he died in war, she is not believed, but if she says that he died on his bed, she is believed;

In famine, she is not believed unless she says that she buried him.

A house that collapsed is like wartime; she testifies by estimation.

When snakes and scorpions are rampant this is like wartime; she testifies by estimation.

Version #1: Pestilence is like wartime; she testifies by estimation;

Version #2: It is not like wartime. She relies on what people say, 'There can be seven years of pestilence, and a man does not die before his time.'