The Lord appeared to Abraham by the oaks of Mamre, as he sat at the entrance of his tent in the heat of the day.
References for Genesis 18:1
He looked up and saw three men standing near him. When he saw them, he ran from the tent entrance to meet them, and bowed down to the ground.
He said, "My lord, if I find favor with you, do not pass by your servant.
Let a little water be brought, and wash your feet, and rest yourselves under the tree.
Let me bring a little bread, that you may refresh yourselves, and after that you may pass on—since you have come to your servant." So they said, "Do as you have said."