Parashas Vayeira · Passuk 18:18
And Avraham shall surely become a great and mighty nation, and all the nations of the earth shall be blessed through him.
Torah Temimah points to Yerushalmi Avodah Zarah 2:1.
TT lemma: ואברהם היו יהיה.
Sefaria — Yerushalmi Avodah Zarah
English: “And Avraham shall surely become…” Rabbi Nachman said in the name of Rabbi Mana: The world cannot endure with fewer than thirty righteous people like Avraham our father. What is the reason? “And Avraham hayo yihyeh”—the word “yihyeh” has the numerical value of thirty.
Derash on the verse (Yerushalmi / gematria) — not a formal named middah of the 13. The word “yihyeh” is valued at thirty.
The world requires at least thirty righteous people of Avraham’s caliber; the gematria of “yihyeh” supplies the number.