Commentaire sur Le Lévitique 7:7

תורה אחת להם [AS THE SIN OFFERING IS SO IS THE GUILT OFFERING:] THERE IS ONE LAW FOR THEM in this (the following) respect:

there is a common denominator between the chatat and the asham sacrifice. While the former atones for inadvertently committed sins for which the karet penalty would be in place if the sin had been committed deliberately, the asham, although not atoning for this kind of sin, does have a similar place in the pyramid of offerings, seeing the sin it atones for involves careless behaviour vis a vis matters that are holy, something that one needs to be more than usually careful about. Symbolically speaking, i.e. as to their “Torah,” they have much in common, תורה אחת.

The one who is fit to [accomplish] atonement. Meaning: The phrase “One law applies to them both” is connected to the phrase following, “the kohein who will bring about atonement ...” for if it meant to equate the sinoffering and guilt-offering [this cannot be,] since it is already written: “As the sin-offering is, so is the guilt-offering,” in which they are equated.

that הכהן אשר יכפר בו THE PRIEST WHO MAKETH EXPIATION THEREWITH — i.e., who is fitted to effect expiation, shall have a share in it, thus excluding an unclean person who has bathed on a particular day but is awaiting sunset to be perfectly clean, one who lacks atonement (an unclean person who has bathed but has to await the next day to bring the sacrifice requisite for his complete restoration to cleanness), and one who is in the state of mourning during the period between the death and the burial of a near relative (Sifra, Tzav, Chapter 9 1).

Excluding a טבול יום (one who has entered a mikveh, but who has to wait for sunset to become ritually pure). Meaning: the sunset has not yet come.