Chullin 82 - 88
Sell and Tell
The Torah prohibits slaughtering an animal and her offspring on the same day. One who purchases an animal for slaughter need not, however, be concerned that perhaps its mother or child was slaughtered that very day. Neither is it incumbent on one who sells an animal for slaughter to inform the next customer that he today sold its mother or child, because he has no reason to assume that the first customer intends to slaughter the animal he bought on the day of purchase.
There are, nevertheless, four days in the year when it is customary for Jews to slaughter animals for meat, and the seller must therefore inform the second customer that there is a strong probability that the mother or child of the animal he purchased is being slaughtered that day by the first customer. These days are: 1) Erev Rosh Hashana; 2) Erev Pesach; 3) Erev Shavuos; and 4) Erev Shmini Atzeres. On these days Jews slaughter animals in order to celebrate the upcoming holiday by eating meat.
Conspicuously missing from the list are two other days preceding holidays - the one before the Seventh of Pesach and the one before the first day of Sukkos. Why?
The Seventh of Pesach is merely an extension of the Pesach Festival which has already been amply celebrated, while Shmini Atzeres at the end of Sukkos is considered a separate holiday, and is therefore a cause for greater celebration. As regards the first day of Sukkos, Tosefos points out that Jews are so preoccupied with preparing the sukkos they are going to inhabit and the lulav and esrog they are going to shake, that they simply don't have time to slaughter animals on the day before the Festival.
- Chullin 83a
Dust and Ashes
In the merit of Avraham expressing such extreme humility in his statement (Bereishis 18:27) that "I am but dust and ashes" his descendants were given the benefit of two mitzvos connected with those lowly elements - the ashes of the Red Heifer which restore purity to one who has been spiritually contaminated by contact with the dead, and the dust used in the potion for miraculously proving the innocence of a married woman suspected of infidelity.
As the commentaries point out, this does not mean that if Avraham had not made that statement there would not have been an opportunity for Jews to restore their purity, or that a man would go on living with a suspected adulteress. Certainly Hashem would have enabled a Jew who had contact with the dead to regain his purity and reenter the Beis Hamikdash just as He prescribed purification for other forms of ritual impurity. But the severity of this form of impurity would have required much more elaborate means to achieve the necessary cure. It was Avraham's humility which won for his descendants the opportunity of achieving this cure with something as comparatively simple as ashes.
In regard to the suspected adulteress, had not Avraham made his self-effacing comparison to dust the rule might have been that wherever a strong suspicion of infidelity existed the marriage would be dissolved, as is the rule today when we have no Beis Hamikdash. It was as a reward for Avraham comparing himself to dust that his children were given an opportunity during the time of the Beis Hamikdash to save the marriage by proving the innocence of the suspected wife through her drinking of a potion containing dust from the Sanctuary floor.
- Chullin 88b