TT #608 · Parashas Ki Seitzei · Sixth / Seventh Aliyah · Passuk 24:21
When you gather the grapes of your vineyard, you shall not pick it over again; it shall be for the stranger, the orphan, and the widow.
Torah Temimah points to Sifrei Devarim 285 / Peah.
TT lemma: לֹא תְעוֹלֵל אַחֲרֶיךָ.
Sefaria — Sifrei Devarim 285 / Peah
English: ‘You shall not pick it over again’ – you shall not take the olelot (the small remaining clusters).
Derash on olelot (Sifrei) — the leftover small clusters are reserved for the poor.
After the main grape harvest one may not return to take the olelot; those clusters belong to the stranger, orphan, and widow.