What does Genesis 18:1 mean?
An unexpected encounter between Abraham and the Lord begins with this verse. It is very different from God's appearance to Abraham in the previous chapter. This time, Abraham may not even be aware, at first, that one of the three men standing near his tent is the Lord in human form.When the Lord takes human form to interact with people on earth, Bible scholars call it a theophany. Given the second revelation about the birth of Isaac the Lord will give, this appearance cannot have come long after the one in Genesis 17.
Abram is living near Hebron, by the oaks of Mamre, the area first mentioned in Genesis 13. The heat of the day, the middle of the afternoon, would have been a time of rest for most people living in this desert region. Abraham was sitting at the door of his tent, likely waiting for the sun to grow less intense before continuing his day.