Sefer HaChinuch ספר החינוך

To not leave over from the festive (chagigah) sacrifice to the third day: To not leave over anything from the festive sacrifice of the fourteenth day until the third day — and that is the sacrifice that comes with the Pesach [sacrifice] to increase the joy — but rather to eat it all within two days, which are the fourteenth and fifteenth. And about this is it stated (Deuteronomy 16:4), “and none of the meat of what you slaughter on the evening of the first day shall be left to the morning.” And the received (traditional) understanding came upon this (Pesachim 71a) that the verse is speaking about the festive [sacrifice] that comes with the Pesach, [to say] that the time of its eating is up to two days. And about this festive [sacrifice], Scripture stated (Deuteronomy 16:2), “And you shall slaughter the Pesach to the Lord, your God, flock and cattle” — meaning to say, that with the Pesach, he brings another sacrifice; meaning to increase the joy.

From the roots of the commandment is the fixed foundation that we have about the commandment of the matter of the Pesach [sacrifice], which is a strong commandment and foundation in our Torah. And hence we were commanded to make the day of its slaughtering a day of joy; and there is no complete joy for people without the proliferation of meat. And this is [the reason for] that which we have been commanded not to leave over at all to the third day from all of the meat that is slaughtered in honor of the joy of the Pesach. But rather, all of it must be eaten on its day, to increase upon it the gladness and the satiation of joyous occasions. And that which is said here is besides the reason that is written about leaving over [sacrifices in general] in the Order of Tsav (Sefer HaChinukh 143), which “gives a reason (or, taste) for the better,” in all of the prohibitions of notar, that which is left over.

From the laws of the commandment is that which they, may their memory be blessed, said (Pesachim 70a) that a man has not fulfilled his obligation of the festive [sacrifice] of the festival — which is also a positive commandment — with the festive [sacrifice] of the fourteenth, as is written in Mishpatim on the commandment to celebrate the festivals (Sefer HaChinukh 88). But he does fulfill his obligation with it for the obligation of the joy of the festival — which is also a positive commandment [as well] — as we have written in this Order (Sefer HaChinukh 488); as the content of the obligation of joy is only to increase meat in order to rejoice, and behold, there is meat [in this]. And from this reason, they, may their memory be blessed, said (Chagigah 7b) that we have fulfilled the [commandment of the] peace-offerings of joy even with a [sacrifice that is the fulfillment of a] vow or oath of peace-offerings, and even if we slaughtered them before the festival — so long as he eats from them during the festival. As one does not have to slaughter the peace-offering of joy at the time of the joy. And one also need not slaughter them for the sake of the peace-offerings of joy — as the essence of the commandment is only to increase the joy with meat, as we have said. And [this] and the rest of its details are elucidated in Tractate Chagigah and in [various] places of Tractate Pesachim.

And this commandment is practiced at the time of the [Temple] by males and females; as even women are obligated in peace-offerings of joy — even though [they are] caused by time — just as they are obligated in resting on [the festival of which it is a part]. And one who transgresses it and leaves over anything from this festive sacrifice to the third day is obligated to burn it with fire, as is the law with that which is left over. And hence there is no liability for lashes for this positive commandment, since it is rectified by a positive commandment — from the principle known to us about this.