Halakhah for Pesachim 185:7

That is that He commanded us that whoever was prevented from slaughtering the first Pesach-offering, slaughter the second Pesach-offering. And that is His, may be exalted, saying, "They shall offer it in the second month [...] at twilight" (Numbers 9:11). And here there is room for the questioner to challenge me, "Why do you count the second Pesach-offering? That contradicts what you have prefaced in the Seventh Principle, when you said that a law of a commandment is not counted as a separate commandment!" The questioner of this challenge should know that the Sages already argued about whether the second Pesach-offering is a law of the first, or a distinct command. And the legal decision was that it is a command stated on its own. So therefore it is appropriate to count it separately. In the Gemara (Pesachim 93a), they said, "'One is liable for excision for [not observing] the first, and one is liable for excision for [not observing] the second.' These are the words of Rabbi (Yehuda HaNasi). Rabbi Natan says, 'One is liable for excision for [not observing] the first, but one is exempt from excision for [not observing] the second.' Rabbi Chananiah ben Akaviah says, 'Even for [failing to observe] the first, one is only liable if he did not fulfill the second.'" And the Talmud [then] asked and said, "With regard to what do they disagree? Rabbi holds that [the second Pesach] is its own festival, whereas Rabbi Natan holds that it is a redress for the first, etc." Behold we have already made clear, that which we were referring to. And there (Pesachim 93b), they said, "Therefore, one who was volitional about this one and that one" - meaning that he volitionally did not offer the first Pesach-offering nor the second Pesach-offering - "is liable according to everyone; and one was inadvertent about this one and that one, is liable according to everyone. If one was volitional about the first but inadvertent about the second - according to Rabbi and Rabbi Natan, he is liable; according to Rabbi Chananiah ben Akaviah, he is exempt. And likewise, if he was volitional about the first, but sacrificed the second, he is liable according to Rabbi." As according to his opinion, there is no redress for the first. (See Mishneh Torah, Paschal Offering 5, where he writes, "If he was volitional about the first, he should sacrifice the second" - and that is the opposite of what he wrote here.) And the law in this is completely like Rabbi. But women are not obligated in this commandment; as it has already been explained there that the second [Pesach-offering] is optional for a woman. And the regulations of this commandment have already been explained in the Gemara, Pesachim. (See Parashat Behaalotecha; Mishneh Torah, Paschal Offering 5.)