We have already learned that although both Rav Huna and Rav Nachman agree that 'ha'Mezakeh le'Ubar, Lo Kanah', Rav Huna extends this ruling even to after the baby is born, whereas Rav Nachman holds 'Kanah'. We reconcile this with Rav Nachman's own ruling 'ha'Mocher Peiros Dekel la'Chavero, Lo Kanah', even after the fruit has grown - because (unlike the fruit of a tree that has not yet grown) he considers an Ubar to be in the world.

Rav Sheishes holds - that 'ha'Mezakeh le'Ubar, Kanah', even before the baby is born.

In the case of a Ger who dies and the people who seize his property then discover that he has a son, or that the Ger's wife is pregnant, the Beraisa rules - that they are obligated to return whatever they took.

If they then discover that the son died or that the wife miscarried - the Tana rules that whoever seized the property from then on may keep it, but not those who seized it the first time.

Rav Sheishes tries to prove his ruling from the above Beraisa - that an Ubar acquires immediately (otherwise, why should the first set of people not acquire the Ger's property immediately).

Abaye refutes Rav Sheishes' proof however on the grounds that Yerushah that comes by itself, is different. Rava refutes Rav Sheishes' proof - in that it is because when the first set of people seized the property, they did so with reservations, since they were not certain that the Ger's wife would not give birth to a healthy baby. And a Kinyan that is made without Gemiras Da'as (i.e. with reservations) is not a valid Kinyan.

The practical difference between Abaye's answer and that of Rava is either where the first set of people acquired it before hearing that the Ger'a wife was pregnant - or after hearing that the Ubar had died (even though this was not yet the case), and he only died later, in which case they will own it according to Rava, but not according to Abaye.

We learned in the Mishnah in Nidah 'Tinok ben Yom Echad Nochel u'Manchil', which appears to mean - that the baby inherits from his father, and bequeaths it to his paternal brothers

This implies - that an Ubar does not inherit (even a Yerushah), a Kashya on Rav Sheishes.

To answer this Kashya, we cite Rav Sheishes, who establishes the Mishnah differently - to answer the Kashya as to why we need the Ubar at all, seeing as the siblings inherit their father anyway.

So Rav Sheishes explains the Mishnah to mean that the Ubar inherits his mother's property to bequeath it to his paternal brothers. Consequently, the inference 'Yom Echad Ein, Ubar Lo' falls away, since as long as the baby is not yet born, it cannot inherit from its mother, because if the mother died, the Ubar must have died first ...

... and we have a principle that, although an Ubar inherits his father in the grave to bequeath the property to his brothers - this is not the case with someone who inherits from his mother (as we learned in 'Yesh Nochlin').

To reconcile this with a case that actually occurred, where the baby shuddered three times after the mother had died - Mar bar Rav Ashi explains that the shuddering of a baby after its death (known as 'Pirchus') is no more a sign of life than the shuddering of a lizard's tail after it has been cut off.

Mar B'rei de'Rav Yosef quoting Rava, establishes the Mishnah in Nidah currently under discussion ('Tinok ben Yom Echad Nochel u'Manchil') with regard to the Cheilek Bechorah, and what the Tana means is that - the moment a baby is born, he detracts from the Cheilek Bechorah.

In the previous case however, the Tana will hold - that it is possible for an Ubar to survive his mother.

The Tana nevertheless says specifically 'Tinok ben Yom Echad', and not an Ubar, because he learns from the Pasuk "ve'Yaldu lo" - that only a son who is born detracts from the Cheilek Bechorah, but not an Ubar.

Practically, this means - that if Reuven and Shimon's baby brother Levi, dies after their father, then Reuven does not inherit a double portion of Levi's inheritance, which is split equally between him and Shimon. Whereas if Levi was only born after their father's death, he would inherit two-thirds of Levi's inheritance.

We are now learning in Rava's name that an Ubar acquires, even though Rava himself, on the previous Amud, maintained that he does not (even in the case of a Yerushah). This is - because it is common for an Amora to refute a proof, first this way, then that way, simply to point out that neither proof is irrefutable.

That is how they quoted Mar b'rei de'Rav Yosef Amar Rava in Sura. In Pumbedisa, they quoted him as saying - that a B'chor does not acquire a double portion in his father's property until he is born, from the Pasuk "ve'Yaldu lo".

It is possible for an Ubar who is a B'chor to have a brother - either if he is a twin or if his deceased father had other wives who were also pregnant when he died.

We rule like all three statements of Mar b'rei de'Rav Yosef in the name of Rava.

Rebbi Yitzchak Amar Rebbi Yochanan rules 'ha'Mezakeh le'Ubar, Lo Kanah'. He reconciles this with our Mishnah ('ha'Omer Im Teiled Ishti Zachar ... ', like Rav Nachman asked Rav Huna) - by differentiating between a third person and a father, who (as we have already learned) is closer to his son than anybody else (and who therefore donates to him with a full heart).

Shmuel promised Rav Chanah Bagdesa'ah - ('from Baghdad') that if he would collect ten people, he would rule in front of them - that 'ha'Mezakeh le'Ubar, Kanah'.

We rule however like Rebbi Yitzchak Amar Rebbi Yochanan - with the sole exception of the Ubar's father, as we just explained.

When a certain man promised his wife that all his property would go to the children that she would bear him - his son from his first wife objected.

His father pacified him - by assuring him that he would receive a portion together with them.

We conclude that the subsequent children will not inherit the first son's portion of the father's estate (in spite of our Mishnah, which we just corroborated) - because at that time, the mother was not even pregnant, in which case the children that will be born later are not considered 'in the world' under any circumstances.

We ask whether the son from the first wife will inherit together with them (should the father subsequently die after they are born) or not. Assuming that his second wife bore him three sons, this means that ...

... if he does, he will receive - a quarter of the estate, plus a quarter of what remains after the initial division.

... if he does not - he will receive a quarter of the estate.

Rebbi Avin, Rebbi Meyasha and Rebbi Yirmiyah all hold that the oldest son does receive a portion of the younger son's inheritance. According to Rebbi Avahu, Rebbi Chanina bar Papi and Rebbi Yitzchak Nafcha - he does not.

Rebbi Yirmiyah thought that the Halachah must be like him and his colleagues, rather than like Rebbi Avahu and his colleagues - because the latter were far younger than them, and were therefore like children by comparison.

Rebbi Avahu responded to Rebbi Yirmiyah's theory - by pointing out this was not a matter of age, but of reasoning.

Rebbi Avahu told Rebbi Yirmiyah how he had explained his reason to Rebbi Avin (one of Rebbi Yirmiyah's colleagues) - who had nodded his head in agreement.

He thn\en suggested to Rebbi Yirmiyah to go and ask Rebbi Avin what he had told him.

Rebbi Yirmiyah followed Rebbi Avahu's advice and went to ask Rebbi Avin, who told him that - it was like Reuven informing Shimon that he was giving something to him and a donkey ('K'ni ka'Chamor'), where it is obvious that (bearing in mind that the donor compared the two in one statement), just as the donkey does not acquire, neither does the Shimon ...

... likewise in our case - seeing as the gift was invalid regarding the children of his second wife (who were not yet even conceived), so too, was it invalid regarding the son of his first wife.