Our Parsha opens with Hashem, as we understand, visiting Avraham Aveinu on the 3rd day after Bris Milah, when Avraham was at the height of his pain following the circumcision, as Rashi indicates, “to inquire about his welfare.” (Metsuda Linear Chumash rendering of Rashi on Perek 18, posuk 1)
It’s not like Hashem needed to pay a visit to ascertain Avraham’s actual condition. Hashem is the Creator, The Master, The Ruler over the world who knows and is aware of everything. And so, as Hashem visited to inquire as to Avraham’s wellbeing, Avraham pardoned himself from Hashem when he spotted 3 travellers inviting them into his tent.