(Mishnah): If one slaughtered and did not cover the blood, one who sees this must cover the blood.

If one covered the blood and it became exposed, he need not cover it again;

If the wind (blew earth and) covered it, he must cover it.

(Gemara - Beraisa): "V'Shafach... v'Chisahu" - the one who spills the blood (slaughters) must cover it;

Question: What is the source that if he did not cover it, an onlooker is obligated?

Answer: "Say to Bnei Yisrael" - they are all commanded.

(Beraisa): "V'Shafach... v'Chisahu" - he must cover with what he spilled, i.e. his hand.

He may not cover with his foot, lest Mitzvos be disgraceful in his eyes.

(Beraisa): "V'Shafach... v'Chisahu" - the one who spills must cover it;

A case occurred in which Reuven covered the blood of what Shimon slaughtered. R. Gamliel made Reuven pay Shimon 10 gold coins.

Question: Is this for stealing the Mitzvah, or for depriving him of the Berachah?

From here we can learn the fine for blessing over a meal (to exempt the others, when someone else should have blessed).

Birkas ha'Mazon is only one Mitzvah, but it is four Berachos.

Answer: We can learn from the following story.

A Tzeduki (heretic): Different powers created the mountains and the wind. It says "the One Who formed mountains and the One Who created wind."

Rebbi: The end of the verse says "Hash-m Tzevakos Shemo" (He created both.)

The Tzeduki requested three days to respond. Rebbi fasted those three days. When Rebbi was about to end his fast, another Tzeduki informed him that the first one killed himself.

Rebbi invited this man to eat. Rebbi offered him 40 gold pieces if he will decline to drink the wine over which they will say Birkas ha'Mazon. (Ben Yehoyada explains this simply. Tosfos - Rebbi requested that the man not bless out loud to exempt the others. Rashi (according to Ra'ah) - he did not want the man to answer 'Amen' to the blessings, for this is like saying the blessings);

The man declined the money. A Bas Kol announced that 40 gold pieces is the value of Birkas ha'Mazon. To this day, this man's family is among the important families in Rome.

(Mishnah): If he covered the blood and it became uncovered (he is exempt).

Question (Rav Acha brei d'Rava): Why is this different than returning a lost object?

"Hashev" - you mjst return it even 100 times.

Answer (Rav Ashi): "You will cover it" teaches that he need cover only once.

(Mishnah): If the wind covered it (he must cover it).

(Rabah bar bar Chanah): This is only if it became uncovered. If not, he is exempt.

Question: The Mitzvah was Nidcheh (permanently rejected, when it was covered). The Mitzvah should never apply again!

Answer (Rav Papa): This teaches that Dichuy does not apply to Mitzvos.

Question: Why is this different than if the blood was absorbed into the ground?

(Beraisa): If the blood was absorbed into the ground, one must cover it.

Answer: That is when one can see a discoloration where the blood was absorbed.

(Mishnah): If the blood became mixed with water, if it still looks like blood, it must be covered;

If blood was mixed with wine, we view the wine as if it was the same amount of water (and apply the previous law);

If it was mixed with blood (that is exempt from Kisuy, e.g.) of a Behemah or of a Chayah that was not slaughtered, we view it (the exempt blood) as if it were the same amount of water;

R. Yehudah says, blood is not Mevatel (nullify) blood.

If blood spurted afar, or is on the knife, it must be covered;

R. Yehudah says, when is this? It is if there is no other blood (that can be covered). If there is other blood, he is exempt.

(Gemara - Mishnah): If blood (of a Korban) became mixed with water, if it has the appearance of blood, it may be thrown on the Mizbe'ach;

If it was mixed with wine, we view the wine as if it were the same amount of water;

If it was mixed with Chulin blood, we view the Chulin blood as if it was the same amount of water;

R. Yehudah says, blood is not Mevatel blood.

(R. Chiya bar Aba): This is only if the water fell into the blood. If blood fell into water, each drop becomes Batel when it falls in.

(Rav Papa): This does not apply to Kisuy ha'Dam, for Dichuy does not apply to Mitzvos. (Once enough blood falls in to have the appearance of blood, one must cover it.)

(Rav Yehudah): If it looks at all red, it is considered blood for atonement (on the Mizbe'ach), to be Machshir food (to receive Tum'ah), and for Kisuy.

Question: Mishnayos explicitly teach this regarding atonement and Kisuy!

Answer: His Chidush is regarding Hechsher.

Question: Clearly, diluted blood is Machshir!

If it is considered blood, blood is Machshir. If it is considered water, water is Machshir!

Answer #1: The case is, it was diluted with rainwater (which is not Machshir unless one wanted it).

Question: Since he mixed the rainwater with the blood, he showed that he wants it, so the water itself is Machshir!

Answer: The case is, the rainwater fell in the blood by itself.

Answer #2 (Rav Asi of Neharvil): Rav Yehudah discusses the fluid that remains when blood congeals.

(R. Yirmeyah of Difti): If one eats (a k'Zayis of) such blood fluid he is Chayav Kares.

That is only if it came from a k'Zayis of proper blood. (Tosfos ha'Rosh - it is possible that the fluid has a greater volume than the blood it came from.)

(Beraisa): (A Revi'is of) such blood has Tum'as Ohel (whatever is under or over it or over the same roof as it becomes Tamei).

That is only if it came from a Revi'is of proper blood.