Parashas Toldos · Passuk 26:33
He named it Shivah; therefore the name of the city is Be’er-sheva to this day.
Rashi on Bereishis 26:33 (classical source on this passuk; not listed as a numbered Torah Temimah unit here).
Lemma / focus: שבעה.
English: After the name of the covenant (the oath).
Derash on the verse (Rashi) — not a formal named middah of the 13: Shivah is linked to the swearing of the covenant.
He named the well Shivah after the oath of the covenant; that is why the city is called Be’er-sheva to this day.