Parsha Mitzvot: Shofetim: Mitzvah 495 – Concept 274
“This shall be the due of the Kohanim from the people, from those who perform a slaughter, whether of an ox or of the flock; he shall give the Kohen the foreleg, the jaw and the maw.” (Deuteronomy 18:3) We are commanded to give the shoulder, two-cheeks and stomach of a slaughtered animal to a Kohen. (Rambam, Hilchot Bikkurim U’sh’ar Matnot Kehuna – The Laws of The First Fruits and Other Kohanic Gifts)
The significance of just these parts of the animal being given to the Kohen is as follows; the foreleg represents the hand. The Torah, when describing Pinchas’ deed (Numbers 25:7), which saved the people of Israel, writes, “He took a spear in his hand.” The hand which performed the deed qualifies for the foreleg of the animal.
The cheekbones symbolize the organ used for prayer. Pinchas prayed as we know from Psalms 106:30.
Finally, the stomach is the organ which suffered the fatal blow as described in Numbers 25:8.
Maimonides in Moreh Nevuchim (3:39) describes all three of these organs as being “Reishit,” something primary of the particular parts of the body. (Rabbeinu Bachya – Commentary To The Torah.)