Parashas Chayei Sarah · Passuk 23:11
“No, my lord, hear me: I give you the field, and I give you the cave that is in it; in the sight of the children of my people I give it to you; bury your dead.”
Rashi on Bereishis 23:11 (classical source on this passuk; not listed as a numbered Torah Temimah unit here).
Lemma / focus: לא אדני / נתתי לך.
English: “No, my lord” — you are not to buy it with money. “I have given it to you” — see, it is as though I have already given it to you.
Derash on the verse (Rashi) — not a formal named middah of the 13: the perfect tense is taken as a formal declaration of gift before the later weighing of silver.
Ephron first presents the field and cave as already given, not as an object of purchase; only later does the transaction become a sale of four hundred shekels.