Rif Beitza 1b {Beitza 3b continues; 4a - 4b}

1b

{Beitza 3b continues}
The weekday {may/does} prepare for Shabbat, and the weekday {may} prepare for Yom Tov, but Yom Tov may not prepare for Shabbat, and Shabbat may not prepare for Yom Tov.

Abaye said: But now, Yom Tov by itself {and not following Shabbat, if the egg was laid on it} should be permitted! A decree upon Yom Tov in general because of Yom Tov which falls after Shabbat. {If it was laid on} Shabbat in general it should be permitted! A decree because of Shabbat after Yom Tov.

He {Abaye} said to him: And do we indeed decree? But they learnt {in a brayta}: If one slaughters a hen and finds within her completed eggs, it is permitted to eat them on Yom Tov.
And if this is so, let us decree {on these unlaid eggs} because of those which are laid on their day!
He {=Rabba} said to him: Completed eggs in their mother's womb are something which is uncommon, and something which is uncommon the Sages did not decree upon.

{Beitza 4a}
It was stated {by Amoraim}:
Shabbat and Yom Tov {one after the other}:
Rav said: That which is laid on this one is forbidden on that one.
And Rabba Yochanan said: That which is laid on this one is permitted on that one.

And they argue in specifically this hachana of Rabba.
{Beitza 4b}
And we rule like Rav, for Rava said: The halacha is like Rav in these three, whether leniently or stringently. One, this that we have said. And another, this that was stated {by Amoraim}: The two days of Yom Tov of exile {the second one because of doubt as to the day}, Rav said: what was laid on this one is permitted on that one, and Rav Assi said: That which was laid on this one is forbidden on that one. And another, this that was stated {by Amoraim}: The two days of Yom Tov of Rosh haShana, Rav and Shmuel both say that if it was laid on this it is forbidden on that.