Rashi

וירא אליו AND THE LORD APPEARED UNTO HIM to visit the sick man. R. Hama the son of Hanina said: it was the third day after his circumcision and the Holy One, blessed be He, came and enquired after the state of his health (Bava Metzia 86b) באלוני ממרא BY THE TEREBINTHS OF MAMRÉ — It was he (Mamre) who advised him (Abraham) regarding the circumcision and therefore He revealed himself to him in his (Mamre’s) territory (Genesis Rabbah 42:8). literally, יֹשֵׁב WAS SITTING — The word is written ישב (without the ו) and therefore may be translated “he sat”: He wished to rise, but the Holy One, blessed be He, said to him, Sit and I will stand. You shall form an example to your descendants — that I, in time to come, will stand in the assembly of the judges while they will sit, as it is said, (Psalms 82:1) “God standeth in the assembly of the judges” (Genesis Rabbah 48:7) פתח האהל AT THE TENT-DOOR — that he might see whether anyone passed by, and invite him into the house כחום היום IN THE HEAT OF THE DAY — The Holy One, blessed be He, brought the sun out of its sheath that he might not be troubled by travellers, and when He perceived that he was grieved that no travellers came He brought to him angels in the form of men (Bava Metzia 86b).