(Mishnah): If Reuven said 'Ploni (a stranger) will inherit me', and he has a daughter, or he said 'my daughter will inherit me', and he has a son, this does not take effect;

R. Yochanan ben Brokah says, it takes effect if he gives to someone who could inherit him.

(Gemara) Inference: It does not take effect because he chose a stranger when he has a daughter, or a daughter when he has a son, but had he chosen one of his daughters (when he has no sons) or one of his sons to inherit everything, it would take effect!

Question (Seifa - R. Yochanan ben Brokah): It takes effect only if he gives to someone who could inherit him;

This is like the first Tana!

Suggestion: Perhaps R. Yochanan ben Brokah says that it takes effect even regarding a (more distant) relative to inherit in place of a daughter, or a daughter in place of sons.

Rejection (Beraisa - R. Yishmael, son of R. Yochanan ben Brokah): Chachamim and my father did not argue about a relative in place of a daughter, or a daughter in place of sons. All agree that the stipulation does not take effect;

They argue in a case that he stipulates that one daughter will inherit in place of all the daughters, or one son in place of all the sons. My father says that it takes effect, and Chachamim say that it does not.

Answer #1: Since R. Yishmael says that they did not argue, we infer that the first Tana (of the Beraisa) says that they did argue (and the Tana of our Mishnah also says so).

Answer #2: R. Yochanan ben Brokah taught the entire Mishnah. It is abbreviated. It means as follows: if one said 'Ploni will inherit me', and he has a daughter, or 'my daughter will inherit me', and he has a son, this does not take effect;

Inference: Had he said 'this daughter will inherit in place of all the daughters', or 'this son in place of all the sons', it takes effect;

This is R. Yochanan ben Brokah's opinion, that if he bequeaths to someone who could inherit him, it takes effect.

(Rav Yehudah and Rava): The Halachah follows R. Yochanan ben Brokah.

(Rava): R. Yochanan ben Brokah learns from "b'Yom Hanchilo Es Banav" - the Torah allows the father to bequeath to anyone he wants.

Question (Abaye): We learn that from "Lo Yuchal Levaker" (he cannot command that a regular son will inherit like the firstborn should, but he can bequeath as he wishes among his sons)!

Answer: We need that verse for the following law.

(Beraisa - Aba Chanan): We know that the inheritance of a regular son is stronger than the extra portion of a firstborn. The former is collected from Ra'uy (property that was destined to come to the father), and the latter applies only to Muchzak (what the father had when he died);

"B'Yom Hanchilo Es Banav" - a father can bequeath to any son he wants.

Suggestion: Perhaps all the more so, he can give the extra portion of the firstborn to another son!

Rejection: "Lo Yuchal Levaker" teaches that he cannot.

Question: The Torah should have said only "Lo Yuchal Levaker", and we would have inferred that he cannot give the extra portion to another son, but he can bequeath the regular portions as he wishes!

Answer: We would have learned a Kal va'Chomer. Inheritance of the extra portion is weaker than that of a regular portion (as we said above), and the father cannot transfer it. All the more so, he cannot transfer a regular portion!

Therefore, we need "b'Yom Hanchilo Es Banav."

(R. Zerika citing Rav): The Halachah follows R. Yochanan ben Brokah.

R. Aba: (A case occurred, and) Rav ruled like R. Yochanan ben Brokah.

Question: What do they argue about?

Answer: They argue about which is preferable (to rely on): a Chacham who taught a Halachah, or a ruling given in an actual case.

(Beraisa): We do not learn the Halachah from what was taught that or from a ruling, unless the Rebbi said 'this is the Halachah in practice'.

If one asked and was told 'this is the Halachah in practice', he may apply it, but he may not compare one case to another.

Question: What does this mean? We always compare one case to another!

Answer (Rav Ashi): It refers to Treifos;

(Beraisa): In Treifos, we do not compare similar cases, for if an animal is cut in one place, it can live, but if it is cut in another place, it will die.

Rav Asi (to R. Yochanan): When you tell us the Halachah, may we act on it?

R. Yochanan: You may not, unless I say 'this is the Halachah in practice.'

Rava (to Rav Papa and Rav Huna brei d'Rav Yehoshua): If my rulings (written down) come before you (in cases) and you have questions against them, do not tear them up until you come to me. If I cannot answer, then I will retract;

If my rulings come before you after my death and you have questions, do not tear them up - perhaps I could have answered them;

Do not learn from them to other cases. A judge can rule only according to what he sees (and understands).