Adam Clarke on Exodus 29:34

Burn the remainder with fire - Common, voluntary, and peace-offerings, might be eaten even on the second day; see Lev 7:16; Lev 19:5, Lev 19:6. But this being a peculiar consecration, in order to qualify a person to offer sacrifices for sin, like that great sacrifice, the paschal lamb, that typified the atonement made by Christ, none of it was to be left till the morning lest putrefaction should commence, which would be utterly improper in a sacrifice that was to make expiation for sin, and bring the soul into a state of holiness and perfection with God. See Clarke's note on Exo 12:10.