Parashas Toldos · Passuk 25:31
Yaakov said, “Sell me your birthright, as this day.”
Rashi on Bereishis 25:31 (classical source on this passuk; not listed as a numbered Torah Temimah unit here).
Lemma / focus: מכרה כיום.
English: As the Targum: as this day—just as this day is clear, so sell me a clear sale. Your birthright—because the [Temple] service belonged to the firstborn.
Derash on the verse (Rashi / Targum) — not a formal named middah of the 13: “as this day” is fixed as a demand for unambiguous transfer of the birthright-service.
Yaakov required a clear sale of the birthright that day, because the sacred service then belonged to the firstborn.