TT #2 · Parashas Vayeira · Passuk 18:1
Hashem appeared to him by the terebinths of Mamre; he was sitting at the entrance of the tent as the day grew hot.
Torah Temimah points to Bava Metzia 86b. E-Daf · Sefaria — Bava Metzia 86b
TT lemma: וירא אליו ה'.
“And Hashem appeared to him.” Rabbi Chama son of Rabbi Chanina said: That day was the third day after his circumcision, and the Holy One, blessed be He, came to inquire after his welfare.
Derash on the verse (Bavli sugya) — not a formal named middah of the 13. The timing of the appearance is fixed by the known chronology of recovery from circumcision.
Hashem visited Avraham on the third day after circumcision—the day of greatest weakness—teaching the importance of timely care for the convalescent.