At the beginning of the Torah portion, Abraham, sitting outside his tent, sees three guests whom he invites to his home. They inform him of the future birth of Isaac. The Sages depict the incident, emphasizing the extent to which Abraham sought the opportunity to fulfill the mitzva of hospitality.

“The Lord appeared to him in the plains of Mamre, and he sat at the entrance of the tent as the day grew hot” (Genesis 18:1). What is the meaning of the phrase, “as the day grew hot”? Rabbi Hama son of Rabbi Hanina said: That day was the third day after Abraham’s circumcision, [a particularly painful day], and the Holy One, blessed be He, came to inquire about the well-being of Abraham. The Holy One, blessed be He, took the sun out of its sheath so that its heat would be felt more intensely so as not to burden the righteous one, Abraham, with caring for guests, [as people would refrain from traveling in the heat]. Abraham sent Eliezer his servant to go outside to look for guests. He went out but did not find any. Abraham said: I don’t believe you…. He went out himself; He saw the Holy One, blessed be He, who was standing at the entrance. That is what is written: “Please do not depart from upon your servant” (18:3). Who were the “three men” who then approached? Mikhael, Gavriel, and Raphael, three angels. Mikhael – who came to bring tidings to Sarah about Isaac’s upcoming birth; Raphael – who came to heal Abraham; Gavriel – who was going to destroy Sodom. (Bava Metzia 86b)