And the 57th mitzvah is that one who was unable [to bring] the Pesach offering is commanded to slaughter the second Pesach offering.1

The source of this commandment is G‑d's statement2 (exalted be He), "[Any person who is impure or far away3...] He shall bring it on the after­noon of the 14th of the second month."

One who is so inclined could challenge me here4 by asking, "Why do you count the second Pesach offering [separately], in contradiction to your Seventh Introductory Principle, where you said that the [individual] laws relating to a single commandment are not counted as separate commandments?"

One who asks such a question should realize that our Sages already disagreed as to whether the second Pesach is included in the laws of the first Pesach or whether it is a separate command­ment. The halachic ruling is that it is a separate commandment, and is therefore counted individually.

Our Sages said in tractate Pesachim,5 "'One is punished by kares [for not bringing an offering] on the first [Pesach] and one is punished by kares [for not bringing an offering] on the second [Pesach].' These are the words of Rebbi [Yehuda HaNasi]. Rabbi Nasan says, 'One is punished by kares [for not bringing an offering] on the first [Pesach] and one is exempt [for not bringing an offer­ing] on the second [Pesach].' Rabbi Chananya ben Akavya says, 'One is exempt even [for not bringing an offering] on the first [Pesach] unless he did not bring the second [Pesach].'" The Talmud then asks, "What is the basis of their disagreement? Rebbi holds that the second [Pesach] is a separate holiday. Rabbi Nasan holds that the second [Pesach] is to make up for the first." This explains clearly what I alluded to above.6

It says there, "Therefore, one who acted intentionally in both," — i.e. intentionally did not bring the first Pesach offering nor the second Pesach offering — "is guilty according to all opinions. One who acted unintentionally in both is exempt according to all opin­ions. One who acted intentionally in the first and unintentionally in the second, is guilty according to Rebbi and Rabbi Nasan, and exempt according to Rabbi Chananya ben Akavya." Rebbi holds that he is guilty even if he acted intentionally on the first and actu­ally brought the offering on the second. This is because he does not hold that the second is to make up for the first.

The halachic conclusion in all these cases is in accordance with Rebbi.7

Women are not obligated in this commandment, as it explains there,8 "Women are permitted [but not obligated] in the second [Pesach offering]."9

The details of this mitzvah are explained in tractate Pesachim.