Rava said: Come and hear a resolution to this dilemma from the mishna: If he discovered he was impure before he shaved, he negates the days of his naziriteship in either case. The Gemara seeks to clarify this: What are the circumstances of this case? When exactly did he find out about the impurity? If it became known to him during the full term of his naziriteship, need this be said, that he negates the previous days? After all, he has yet to complete his naziriteship vow. Rather, is it not referring to a case when the impurity was discovered after the full term of his naziriteship? Conclude from the mishna that he negates the days of his naziriteship even if he discovered the impurity after the completion of his term.

The Gemara continues to analyze the aforementioned case. And you can still raise the dilemma: Does he negate the entire period of his naziriteship or does he negate just seven days? The Gemara asks: According to whom is this dilemma raised? If we say this dilemma is referring to the opinion of the Rabbis (see 16b), it is obvious that he negates it all, as they maintain that even a nazirite who becomes impure after the completion of his naziriteship must observe another thirty days. And if it is referring to the opinion of Rabbi Eliezer, his ruling with regard to any impurity after the full term of his term is that one negates only seven days.

The Gemara responds: The one who raised this dilemma could have said to you: This statement of Rabbi Eliezer that a nazirite negates a mere seven days applies only if he became impure after the full term of his naziriteship, but this one became impure before the end of the full term, and therefore he negates the entire period. Or perhaps it is different here, as it is a case of knowledge that came to light after the full term of his naziriteship.

The Gemara answers: And one can resolve the dilemma from this mishna itself. The mishna teaches that if the nazirite discovered he was impure before he shaved he negates his naziriteship in either case. And it does not distinguish between cases where this happened before the end of the full term or after it. This indicates that in any case he negates only seven days.

§ The Sages taught (Tosefta, Zavim 2:8): In the case of one who finds a corpse lying across the width of a road, with regard to teruma the passerby is impure. But with regard to both a nazirite and one performing the ritual of the Paschal offering, the passerby is pure, as it is considered impurity imparted by a grave in the depths. In what case is this statement said, that one is impure with regard to partaking of teruma? It is said in a case where he does not have space to pass by on the road without passing over the corpse.

But if he has space to pass by, then even with regard to teruma he is pure. This is because it is possible that the passerby did not become ritually impure, and there is a principle that if an uncertainty arises concerning the ritual purity of a person or item in the public domain, the person or item is considered pure.

Similarly, in what case is this statement said? It is said in a case where one finds the corpse whole. However, if it is broken or dismembered he is pure, even if there is no space to pass by. The reason is that we suspect that perhaps he passed between the parts of the corpse and did not touch or pass over any of them. This applies when he finds the corpse out in the open. But if he finds it in a grave, even if it is broken or dismembered, he is impure. This is because the grave joins the parts into one unit and renders him impure if he passed over any part of the grave, even if he did not pass over part of the corpse.

The baraita adds: In what case is this statement said, i.e., that if the corpse was dismembered the passerby is pure? It is said with regard to a passerby who travels by foot. However, if he was loaded with a heavy burden or was riding an animal, he is impure. This is because in the case of one who travels by foot, it is possible that he will not touch the corpse and will not move it and will not pass over it, whereas in the case of one who is loaded with a heavy burden and therefore does not walk in a straight line, or one riding an animal, it is impossible that he will not touch the corpse and will not move it and will not pass over it.

In what case is this statement said, that a nazirite and one bringing a Paschal offering are considered pure? It is said with regard to impurity imparted by a grave in the depths. However, if the source of impurity was known to others but not to the individual who became impure, all three of them, i.e., a nazirite, one performing the ritual of the Paschal offering, and the one who wishes to partake of teruma, are impure.

The baraita continues: And which corpse is considered to impart impurity of the depths? Any corpse of which no one is aware, even at the end of the earth. But if even one individual is aware of it, even if that person is at the end of the earth, this is not considered impurity imparted by a grave in the depths.

The baraita continues: To ascertain whether anyone ever knew about the corpse, its condition is taken into account. If the body was concealed in hay or in pebbles, so the person might have died in an avalanche, it is likely that the corpse had never been found; this is impurity imparted by a grave in the depths. However, if it was found in water, or in a dark place, or in the clefts of the rocks, this is not impurity imparted by a grave in the depths. Although these are places where people do not often go, with the passage of time the corpse is likely to be discovered, and it is quite possible that someone already passed by and saw it.

The baraita concludes: And the Sages said that the leniency of impurity imparted by a grave in the depths applies only with regard to a corpse, but not with regard to other sources of impurity.

§ The mishna taught: How does one differentiate between a known and an unknown impurity? If a nazirite descended to immerse in a cave, and a corpse was found floating at the mouth of the cave, he is impure. The Gemara comments: A floating impurity does not render a person or item impure in the case of a carcass of a creeping animal. As it is taught in a baraita (Tosefta, Teharot 5:6): With regard to the case of uncertain impurity, where an item might have touched something impure that was floating, either in water in a vessel or in water in the ground, e.g., a well, the item is pure. Rabbi Shimon says: If the impurity was floating in water that was in a vessel, the item is impure; if the impurity was in water in the ground, it is pure.