Genesis 18:1 - 33
ESV - 1 And the Lord appeared to him by the oaks of Mamre, as he sat at the door of his tent in the heat of the day. 2 He lifted up his eyes and looked, and behold, three men were standing in front of him. When he saw them, he ran from the tent door to meet them and bowed himself to the earth
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.