that we examine a beit haperas that lies in the path to Jerusalem for those offering the Paschal lamb to determine whether there is actually any ritual impurity present, in order to enable those who pass through it to know whether they are still ritually pure and able to offer the Paschal lamb. But we do not examine a beit haperas for the sake of those eating teruma in order that they should be able to eat teruma in purity. The Gemara asks:

What is meant when we say that we examine for those offering the Paschal lamb? Practically, how is it examined? Rav Yehuda said that Shmuel said: One must blow the dust on the path before taking each step in the beit haperas as he walks through it, in order to see if there is a hidden bone there. Rav Yehuda bar Abaye in the name of Rav Yehuda said: A beit haperas that has been trodden underfoot is considered ritually pure, since it is assumed that any bones that were there have been removed or broken. The impurity of a beit haperas is due to a rabbinic decree. The Sages waived this decree in a case where the necessary examination is made, in order to allow people to be able to offer their Paschal lambs. However, this leniency is limited to the case of the Paschal lamb, since its neglect carries the prohibition of karet. It is not extended to other cases, such as the prohibition to eat impure teruma.

MISHNA: One who was ritually impure or on a distant journey and did not observe the first Pesaḥ by participating in the offering of the Paschal lamb on the fourteenth of Nisan should observe the second Pesaḥ by participating in the offering on the fourteenth of Iyyar. If one unwittingly forgot or was prevented due to circumstances beyond his control and did not observe the first Pesaḥ, he too should observe the second Pesaḥ. If so, that the second Pesaḥ is observed even by someone who forgot or was prevented from observing the first Pesaḥ, why is it stated in the Torah that the second Pesaḥ is observed only by one who was ritually impure or on a distant journey? These cases were specified in order to teach that these two groups of people are exempt from karet if they do not observe the second Pesaḥ, but those who were not ritually impure or on a distant journey are liable to receive karet, as the Gemara will explain.

GEMARA: It was stated that the amora’im disagreed about the following issue: If one was on a distant journey and others slaughtered the Paschal lamb and sprinkled its blood on his behalf, and he arrived in time to eat the Paschal lamb, does he need to observe the second Pesaḥ since he was far away at the time that the sacrifice was offered? Rav Naḥman said: His offering was accepted, and he need not observe the second Pesaḥ. Rav Sheshet said: His offering was not accepted, and he must sacrifice the Paschal lamb on the second Pesaḥ. The Gemara explains their opinions. Rav Naḥman said: His offering was accepted because the Torah has mercy on one who was on a distant journey and allows him the option of observing the second Pesaḥ; but if he nonetheless did participate in the sacrifice of the Paschal lamb on the first Pesaḥ, may blessing come upon him. And Rav Sheshet said: His offering is not accepted because the Torah deferred his observance to the second Pesaḥ just as it does for one who is ritually impure. Just as one who is ritually impure may not voluntarily participate in the Paschal lamb, neither may one who is on a distant journey.

Rav Naḥman said: From where do I say my opinion? As we learned in the mishna: One who was ritually impure or on a distant journey and did not observe the first Pesaḥ should observe the second Pesaḥ. The expression: And did not observe, indicates by inference that regarding one who was on a distant journey, had he wished, he could have observed it and would thereby be exempt from participating in the sacrifice of the Paschal lamb on the second Pesaḥ.

And Rav Sheshet said in response: If so, consider the latter clause of the mishna, which teaches: If one unwittingly forgot or was prevented due to circumstances beyond his control and did not observe the first Pesaḥ, he should observe the second Pesaḥ. According to your reasoning, from the fact that it is taught: And did not observe, conclude by inference that had he wished, he could have observed it. However, this is not possible, as the mishna states explicitly that he unwittingly forgot or was prevented due to circumstances beyond his control and was unable to observe the first Pesaḥ.

Rather, the mishna must be explained differently, as follows: Even though it does not say so explicitly, the mishna is teaching with the phrase: And he did not observe, the case of one who intentionally refrained from observing the first Pesaḥ together with the other cases in the mishna. Here, too, in the first part of the mishna, the phrase: And he did not observe, must be understood as including another category of people: It is teaching the case of an acute mourner, i.e., one whose relative died that same day and has not yet been buried, together with the other cases. The first part of the mishna includes three cases: One who was ritually impure, one who was on distant journey, and one who was an acute mourner. Therefore, it cannot be inferred that had he wished to observe the first Pesaḥ, he could have done so.

Rav Ashi said: The mishna is also precisely formulated according to this interpretation, as it teaches: These are exempt from karet, but those are liable to receive karet. To which part of the mishna is this referring? If we say that this statement is referring to one who unwittingly forgot and one who was prevented due to circumstances beyond his control, are one who unwittingly forgot and one who was prevented due to circumstances beyond his control subject to the punishment of karet? One is liable to receive karet only for performing a transgression intentionally. Rather, is it not referring to the case of one who intentionally refrained from observing the Pesaḥ, which is included in the phrase in the latter clause: And he did not observe, and to the case of an acute mourner, which is included in the parallel phrase in the first clause? These two categories of people are liable to receive karet if they fail to sacrifice the Paschal lamb on the second Pesaḥ.

And Rav Naḥman could have said to you in response: Actually, the mishna refers only to the case of one who intentionally refrains from observing the first Pesaḥ and not to the case of an acute mourner; and by right it should have taught this ruling with the expression: He is liable, in the singular. And the reason that it teaches this ruling with the phrase: These are liable, in the plural, is that since the first clause of the mishna teaches its ruling with the expression: These are exempt, in the plural, the latter clause also teaches its ruling with the expression: Those are liable, in the plural. Therefore, the phrase in the first clause: And did not observe the first Pesaḥ, teaches that one on a journey has the option of observing the first Pesaḥ if he wishes. And the same phrase in the latter clause: And did not observe, comes to include the case of one who intentionally refrains from observing the first Pesaḥ.

Rav Sheshet said: From where do I say my opinion? As it was taught in a baraita that Rabbi Akiva says: It is stated that one who is ritually impure on the first Pesaḥ observes the second Pesaḥ, and it is stated that one who is on a distant journey observes the second Pesaḥ;