Genesis 18:2

And he lift up his eyes and looked, and, lo, three men stood by him. It was not a case of a slow approach, but of a sudden appearance. A moment before no one had been in sight, and now three men stood by him, looming over him as he reclined on his chair or couch. And when he saw them, he ran to meet them from the tent-door, and bowed himself toward the ground. As the strangers were still a few steps away, Abraham, with true Oriental hospitality, ran forward to meet them, and since he recognized in one of them the Lord, he bowed down before them in worshipful homage. Two of the visitors were angels, Genesis 19:1; the third was the Lord Himself, Hebrews 13:2, the Angel of the Lord in the peculiar sense of the word, as it is applied to the Son of God in the Old Testament.