Chullin Daf 88 צולין דַף 88

The Mishnah taught, and a Baraisa elaborates: וכסהו – and he shall cover it, מלמד שדם הניתז ושעל הסכין חייב לכסות – this teaches that blood which spattered and blood which is on the knife must be covered. Rebbe Yehudah explains this only applies בזמן שאין שם דם אלא הוא – when there is no blood other than this which can be covered, but if there is, he need not cover this blood. Another Baraisa darshens "וכסהו" to teach שכל דמו חייב לכסות – that all its blood must be covered, including the blood which spattered or which is on the walls of the throat. Rabban Shimon ben Gamliel says this only applies שלא כסה דם הנפש – where he did not already cover the lifeblood, but if he did, he is exempt from covering this blood. These three opinions are explained: the Rabbonon (i.e., the Tanna Kamma of the second Baraisa) hold "דמו" – its blood implies one must cover כל דמו – all of its blood. Rebbe Yehudah holds "דמו" implies אפילו מקצת דמו – even just some of its blood. Rabban Shimon ben Gamliel holds that although all of the obligated blood must be covered (like the Rabbonon), he holds "דמו" implies דמו המיוחד – its unique blood, i.e., its lifeblood.

The next Mishnah lists numerous materials which may be used for כסוי הדם, such as fine dung, fine sand, lime or ground pottery, or a brick or earthenware cover which was crushed. It lists numerous materials which may not be used for כסוי הדם, such as coarse dung or sand, or overturning a כלי onto the blood. Rabban Shimon ben Gamliel stated a general rule: דבר שמגדל בו צמחים מכסין בו – something in which plants can grow may be used for covering blood, but something in which plants cannot grow may not be used for כסוי הדם. Rav Nachman bar Rav Chisda said one must use material שזורעין בו ומצמיח – that one may plant in it and it grows, excluding desert sand, etc. Rava objected to this ruling, but it is supported by a Baraisa teaching that one who shechts in the desert and has no earth to cover the blood should grind a golden dinar and cover it with the dust, indicating that desert sand cannot be used. The Baraisa adds that one traveling on a ship and has no earth to cover blood of his shechitah should burn his garment and cover the blood. The Gemara quotes pesukim calling ashes and gold dust "עפר".

Rava says: בשכר שאמר אברהם אבינו "ואנכי עפר ואפר"  – As reward for Avraham Avinu saying, “I am but dust and ashes,” זכו בניו לשתי מצות – his descendants merited two mitzvos:אפר פרה ועפר סוטה – ashes of the פרה [אדומה], and the earth used for testing a sotah. The mitzvah of כסוי הדם is not mentioned here, because it does not provide a benefit besides the mitzvah itself (as opposed to פרה אדומה, which effects taharah, and sotah waters, which bring marital harmony). On the next Daf, Rava says that in reward for Avraham refusing to accept "מחוט ועד שרוך נעל" – from a thread to a shoe strap, his descendants merited the mitzvos of the thread of techeiles and the strap of tefillin. The Gemara explains the benefits of these mitzvos.