TT #30 · Parashas Vayigash · Passuk 47:22
Only the land of the priests he did not buy, for the priests had a fixed allotment from Pharaoh, and they ate their allotment that Pharaoh gave them; therefore they did not sell their land.
Torah Temimah points to Beitzah 16a.
TT lemma: ואכלו את חקם.
English: From here we learn that “chok” is an expression of food/sustenance.
Derash on the verse (Bavli sugya) — not a formal named middah of the 13.
The word “chok” in this verse denotes a fixed food allotment, establishing its meaning as sustenance.