And the 120th prohibition is that we are forbidden from leaving over any part of the Thanksgiving offering (todah) until the morning [of the next day].

The source of this commandment is G‑d's statement,1 "[It must be eaten on the same day] with nothing left over until the [next] morning." From this offering we derive the principle for the other offerings: that whatever remains after the time designated for their consumption becomes nosar.2 One then is obligated to burn it, since this is a lav she'nitak l'aseh,3 and burning it is a positive commandment, as we explained in Positive Commandment 91.