One who was contaminated or was on a distant journey, and had not observed the First [Pesach], must observe the Second. [If] he erred or was prevented, and [therefore] did not observe the First [Pesach], he must observe the Second. If so, why is it said: One who was contaminated or was on a distant journey (Numbers 9:10)? Because these are exempt from kares, but those are liable to kares.

What is a distant journey? From Modi'in and beyond, or a like distance in any direction —- [these are] the words of R' Akiva.  R' Eliezer says: From the threshold of the Temple Courtyard and beyond.  Said R' Yose: Therefore there is a dot over the letter hei, as if to say, not because it is literally distant, but rather from the threshold of the Temple Courtyard and beyond.

What are the differences between the first pesach and the second? —- The first [pesach] comes under the prohibition of, It shall not be seen and it shall not be found (Exodus 13:7, 12:19), whereas at the second [pesach], [both] matzah and chametz are with him in the house; the first requires the recitation of Hallel during [the pesach's] eating, but the second does not require Hallel during its eating.  Both require the recitation of Hallel when they are offered; [both] are eaten roasted, together with matzah and bitter herbs; and [both] override the Sabbath.

[If] the pesach was offered in a state of contamination, zavim, zavos, menstruants, or women after childbirth may not eat of it; but if they did eat, they are exempt from [the penalty of] kares.  R' Eliezer exempts [them] even [from the kares due] for entering the Temple.