Parashas Vayeira · Passuk 20:7
And now, restore the man’s wife, for he is a prophet, and he will pray for you and you will live; but if you do not restore her, know that you shall surely die, you and all who are yours.
Torah Temimah points to Makkos 9b.
TT lemma: כי נביא הוא.
English: “For he is a prophet.” Does that mean that if he were not a prophet one need not restore her? Rather, this is what He said to him: “Restore the man’s wife.” And as for your claim “Did he not say to me, ‘She is my sister’?”—he is a prophet, and he learned from you: when a guest comes to a city, does one ask him “Is this your wife or your sister?” From here [we learn] that a child of Noach is liable to death for failing to learn what he ought to have learned.
Derash on the verse (Bavli sugya) — not a formal named middah of the 13. The prophetic title is linked to a standard of expected learning for non-Jews.
A Noachide can be held liable for failing to learn what he should have known; Avraham’s prophetic status taught Avimelech the proper way to inquire about a guest’s companion.