Parashas Vayeira · Passuk 22:5
And Avraham said to his young men, “Stay here with the donkey, and I and the lad will go yonder; we will worship and we will return to you.”
Torah Temimah points to Moed Katan 18a.
TT lemma: ונשובה אליכם.
English: “And we will return to you.” Rabbi Yochanan said: From where do we know that a covenant is made with the lips? As it is written, “And we will return to you”—and the matter was assisted, and the two of them returned.
Derash on the verse (Bavli sugya) — not a formal named middah of the 13. A fulfilled prediction is taken as proof of the power of spoken commitment.
A covenant is made with the lips; Avraham said “we will return” and both he and Yitzchak returned, for Heaven assisted the spoken word.