The “door of the tent” is a fold of the lower part of the tent, which is fastened by a loop to the post nearby. It may thus be opened or closed at pleasure. For the sake of light and air, it is generally thrown back during the day.
Noon is the hour of rest among the Orientals. When the sun is at its height, the wind often becomes softer and the heat more oppressive. Then the dwellers in tents may be seen sitting “in the door,” or reclining in the shade of the tent. It is also the hour for dinner. See Genesis 43:16,2516And when Joseph saw Benjamin with them, he said to the ruler of his house, Bring these men home, and slay, and make ready; for these men shall dine with me at noon. (Genesis 43:16)
25And they made ready the present against Joseph came at noon: for they heard that they should eat bread there. (Genesis 43:25). Some travelers say that the Arabs eat by the door of the tent in order to notice the stranger passing by, and to invite him to eat with them. In the case mentioned in the text Abraham had probably dined, and was resting after dinner.