Chabad.org — English translation + Rashi
Torah Temimah points to Menachos 9b.
E-Daf.com — Menachos 9b
HebrewBooks / Shas PDF
English: Remainders that diminished between kemitzah and hakatarah are forbidden to eat, as the verse says “and the remainder from the minchah” — and not the remainder from [already reduced] remainders.
Miyut of depleted shirayim — remainders that shrank between kemitzah and hakatarah may not be eaten.
If the leftover flour is reduced before the kometz is burned, it may not be eaten. The Torah’s language “the remainder from the minchah” is taken to exclude flour that has already been diminished after the handful was removed but before the memorial portion was offered.