And the 91st mitzvah is that we are commanded to burn nosar.1
The source of this commandment is G‑d's statement2 (exalted be He), "What is left over from the meat of the sacrifice on the third day must be burned in fire."
Regarding the Paschal lamb, G‑d A‑lmighty said,3 "Do not leave any of it over until morning. Anything that is left over until morning must be burned in fire." The Mechilta4 says explicitly, "This verse comes to add a positive commandment to the prohibition."
In many places in tractates Pesachim,5 and Makkos6 and elsewhere,7 our Sages say explicitly that the prohibition of nosar is a lav shenitak l'aseh, and one is therefore not punished by lashes for transgressing it.8 The aseh [positive commandment] is, as we said, "Anything that is left over until morning must be burned in fire."
The law of pigul is identical to that of nosar, as will be explained in the Prohibitions.9 This is because pigul is referred to [in Scripture10] as nosar.
The details of this mitzvah as well have been explained in tractate Pesachim11 and in the end of Temurah.12
