Sefer HaChinuch ספר החינוך

To not leave the entrails of the Pesach sacrifice to stay overnight: Not to leave the entrails of the Pesach sacrifice until the morning, [such] that they not be sacrificed, and [so] become disqualified with this leaving over and become called notar (what is left over); as it is stated (Exodus 23:18), “and the fat of My festival offering shall not be left lying until morning.” And the same is true of other portions to be burned in other sacrifices. And the language of Mekhilta DeRabbi Yishmael 23:18 is “‘The fat shall not be left lying’ — the verse comes to teach that the fats are disqualified by lying over.” And this preventing was already repeated in another place, as it is stated (Exodus 34:25), “and the sacrifice of the festival of Pesach shall not be left lying until morning.”

It is from the roots of the commandment [that it is] because it is the honor of a sacrifice to sacrifice it at its time that is set for it. And one who passes the set time appears like one who abandons [it] and throws the matter over his back; and he does not arouse himself and properly place his intentions upon the service. And because of this, [the portions to be burned] become disqualified with it.

From the laws of the commandment — that which they said (Pesachim 64b) that it is a commandment to burn the entrails of each and every sacrifice on its own; that which they said (Menachot 72a), that the commandment of their burning is after their slaughter, close upon [it], and if he did not burn them like this, he can burn them the whole night until the dawn (amud hashachar), and [this is] specifically when the fourteenth of Nissan comes out to be on Shabbat, since the fats of Shabbat [sacrifices] can be sacrificed on a holiday, but if the fourteenth of Nissan fell out to be [a weekday], we do not burn them at night, as we do not burn the fats of [weekday sacrifices] on a holiday, since [the sanctity of a] holiday is a positive and a negative commandment and [so] pushes off the negative commandment of “it shall not be left lying;” and the rest of its details — are found in Pesachim. (See Mishneh Torah, Laws of Paschal Offering 1.)

And [it] is practiced at the time of the Temple by male priests. And one who transgresses it and does not sacrifice them is not lashed, as there is no act [involved] with it.