(Rav Nachman): If one acquires on behalf of a fetus, the fetus does not acquire;

If the giver said 'when she will give birth...', the baby acquires.

(Rav Huna): Even if he said 'when she will give birth...', the baby does not acquire.

(Rav Sheshes): In both cases, the baby acquires.

Support (Rav Sheshes for himself - Beraisa): If a convert died, and Yisre'elim grabbed his property.

If they heard that he left a son, or that his wife was pregnant, they must return it;

If after they returned it, they heard that the son died or that the wife miscarried, the first Kinyanim are void. What anyone takes now, he keeps.

If a fetus did not acquire, the first Kinyanim would be valid (even after they heard that his wife was pregnant)!

Rejection #1 (Abaye): Inheritance is different, for it happens automatically.

Rejection #2 (Rava): There, the initial Kinyanim were invalid (because they did not know whether or not there were heirs).

Question: What is the difference between Abaye and Rava?

Answer: They argue in a case when people heard that the fetus died, grabbed property, and it turned out that the fetus died only after they grabbed, and others grabbed property after the fetus (truly) died. (According to Rava, the first people acquire, for they were sure that there were no heirs. According to Abaye, the second people acquire.)

Question (against Rav Sheshes - Mishnah): A one-day old baby inherits and bequeaths.

Inference: Less than one day (i.e. a fetus) does not inherit!

Answer #1 (Rav Sheshes): A one-day old baby inherits his mother's property to bequeath it to his paternal brothers, but a fetus does not.

Question: Why not?

Answer: The fetus always dies before the mother. A son does not 'inherit' his mother after his own death in order that the property should pass to his paternal brothers.

Question: Is it really true that the fetus dies first?!

There was a case of a fetus that quivered three times after its mother died!

Answer (Mar bar Rav Ashi): Quivering does not show that it is alive. If a rodent's tail is cut off, also it quivers!

Answer #2 (Mar brei d'Rav Yosef): A one-day old baby is considered a son in the calculation of the extra share of the firstborn.

Inference: A fetus does not decrease the extra share of the firstborn. "V'Yoldu Lo" (we consider only sons who were already born when the father died).

Version #1 - Chachamim of Sura (Mar brei d'Rav Yosef): A son born posthumously does not decrease the extra share of the firstborn - "v'Yoldu Lo".

Version #2 - Chachamim of Neharde'a (Mar brei d'Rav Yosef): A firstborn born posthumously does not receive an extra share (e.g. if another son was also born posthumously) - "Yakir" (the father must (be fitting to) make known his firstborn. Here, he was unable to do so).

The Halachah follows Mar brei d'Rav Yosef in these three laws.

(R. Yitzchak): If one acquires on behalf of a fetus, the fetus does not acquire;

Question: The Mishnah says that the fetus acquires!

Answer: The Mishnah discusses a man giving to his son. Because he feels great affinity for his son, he resolves more firmly to give, so the Kinyan works;

In any other case, the fetus does not acquire.

Shmuel expounded in front of 10 people that if one acquires on behalf of a fetus, the fetus acquires.

The Halachah is, if one acquires on behalf of a fetus, the fetus does not acquire.

Yakov told his wife Sarah 'my property is to the sons I will have from you.' His oldest son (Reuven, from a different wife) asked 'what will I get?!' Yakov said 'go acquire like one of her sons.'

Clearly, nothing takes effect now regarding Sarah's (future) sons. They are not yet in the world (she was not even pregnant).

Question: (When Yakov dies,) does Reuven get an extra share of the estate (above his normal share) equal to what he would receive if he were a son of Sarah (and they received all the property)?

Answer #1 (R. Avin, R. Meisha, and R. Yirmeyah): Yes, he gets an extra share.

Answer #2 (R. Avahu, R. Chanina bar Papa, R. Yitzchak Nafcha): He does not get an extra share.

R. Avahu: Does the Halachah follow you, or us?

R. Yirmeyah: The Halachah follows us. We are older than you.

R. Avahu: The Halachah does not depend on age, rather, on reason!

Question (R. Yirmeyah): What is your reason?

Answer (R. Avahu): It is as if he said to him 'acquire like the donkey.' (Since Sarah's sons cannot acquire, and he said 'acquire like her sons', also Reuven does not acquire.)