레위기 2:2 해설: Rashi, Rashbam, Tur HaArokh & Siftei Chakhamim

הכהנים וקמץ [AND HE SHALL BRING UNTO …] THE PRIESTS: AND HE SHALL TAKE A FISTFUL — from the קמיצה (the taking of the fistful) and onwards is the duty of the priesthood (Menachot 9a).

מלא קומצו, our sages in Yuma 47 explain that what the Torah refers to as קומץ is the amount of flour mixed with oil which a priest can hold when he doubles over the three middle fingers of his hands as if making a fist.

וקמץ, “he shall scoop three fingers full;” this is the first part of the procedure that only the priests were allowed to perform. The procedures mentioned up until this point, i.e. the pouring of oil, the adding of frankincense to the flour before handing the mass to the priest could be performed by the owner/donor, even if he was not a priest. There is only one step in the procedure prior to the scooping up by the priest of three fingers full of the mixture, that also necessitated a priest, and this was the presentation of the mass at the southwestern corner of the altar.

וקמץ משם AND HE SHALL TAKE A FISTFUL FROM THERE — from the place where the feel of the layman may stand; and this is stated in order to teach you that the קמיצה is valid at whatever place in the fore-court it is carried out, even in that eleven cubits) which are the area where the feet of the ordinary Israelites may tread (cf. Yoma 16b).