Another Halacha that is mentioned in פרשת אחרי מות, is the law of כיסוי הדם. This refers to our obligation to cover the blood of an עוף, fowl, and a חיה, a non-domesticated animal.
When שחיטה, ritual slaughtering is done on these types of animals, soft dirt or ash, needs to be waiting, that is used to cover the blood.
A ברכה is also recited that ends with the words, על כיסוי הדם.
There is a Midrash that says that the birds are rewarded with this special. This is because they joined together to cover the blood of הבל, after he was murdered by his brother, קין.
This unusual Mitzva is still observed by שוחטים, to this very day.
Ritual slaughtering is allowed on Yom Tov, but only if there is soft soil or ash that is prepared from before the Chag. This is also one of those Mitzvot that very few people ever get to observe.