Chullin Daf 87 צולין דַף 87

The next Mishnah states that if one shechted and did not cover the blood, anyone who sees must cover it. A Baraisa darshens: ושפך...וכסה – and he shall spill its blood and cover it with earth, to teach מי ששפך יכסה – he who spilled the blood of the חיה or עוף should be the one to cover it. If he did not, someone else must cover it, because "ואומר לבני ישראל" – and I say to the children of Yisroel extends the mitzvah to all of Klal Yisroel. The Gemara relates that once, someone shechted and another person preempted him and covered the blood. Rabban Gamliel required him to pay ten זהובים – golden [dinars] to the shochet. The Gemara asks: שכר מצוה או שכר ברכה – Are the ten זהובים payment for the mitzvah he seized, or payment for the berachah recited over the mitzvah? A practical difference is ברכת המזון, which is a single mitzvah composed of four berachos. The Gemara proves that one must pay forty זהובים for reciting ברכת המזון in someone else’s place.

The Mishnah stated: כסהו ונתגלה פטור מלכסות – if one covered [the blood] and it became uncovered, he is exempt from covering it again. Unlike השבת אבדה – returning a lost object, which must be returned even a hundred times, here, the term וכסהו – and he shall cover “it” limits covering the blood to only one time. The Mishnah concluded: כסהו הרוח חייב לכסות – if the wind covered [the blood], he is obligated to cover it. Rebbe Yochanan says this only applies שחזר ונתגלה – where it became uncovered again, but if it remains covered, he is exempt. The Gemara objects: הא אידחי ליה – even if it became uncovered, it was rejected from its mitzvah while it was covered, and he should remain exempt from covering it!? Rav Pappa answers: זאת אומרת אין דיחוי אצל מצות – this tells us there is no permanent rejection regarding mitzvos.

The next Mishnah states that if blood requiring כסוי הדם became mixed with water, אם יש בו מראית דם – if it has the appearance of blood, he must still cover it. If it became mixed with wine, or with blood which does not require כסוי, רואין אותו כאילו הוא מים – we view [the other liquid] as if it were water; if the obligated blood would give that amount of water the appearance of blood, it requires כסוי. Rebbe Yehudah says: אין דם מבטל דם – blood does not nullify blood, and even a minute amount remains obligated in כסוי. A parallel Mishnah discusses blood of korbanos mixed with other liquids (regarding applying the mixture to the מזבח). Rebbe Yochanan said that that ruling only applies where water fell into the blood, but if blood fell into water, ראשון ראשון בטל – each first drop of blood is nullified as it falls into the water, so even if the mixture eventually appears red, it remains disqualified because of דיחוי – rejection. Rav Pappa says this rule does not apply to כסוי הדם, because even if it was temporarily exempt from כסוי, אין דחוי אצל מצות – there is no permanent rejection regarding mitzvos.