Genesis 18:9-10

"And they said unto him, Where is Sarah thy wife? And he said, Behold, in the tent. And he said, I will certainly return unto thee when the season cometh round; and, lo, Sarah thy wife shall have a son. And Sarah heard in the tent door, which was behind him."

Up to this point, the identity of Abraham's guests could have been unknown, but, with this interchange, both Sarah, and certainly Abraham, knew the supernatural nature of their guests. It had been only a short while since the name had been given to Sarah, yet "He" knew it; also "He" knew of their desire for a son, and apparently also, that God had promised that Sarah would be the mother. Therefore, we are unwilling to excuse Sarah's unbelieving laughter, a little later, on the basis that: "For all Sarah knew, the promise of a child was merely a gesture made by meddlesome travelers; her impetuous reaction was one of derision."[15] Nevertheless, we cannot fault Sarah as being faithless, for the writer of Hebrews declared that, "By faith, even Sarah herself, received power to conceive a seed when she was past age" (Hebrews 11:11). Whatever Sarah's initial impression might have been, she was promptly to receive concrete and convincing evidence that God Himself was their guest.

"And they said unto him ... And he said, I will certainly return ..." In the first clause, what the principal one of the guests said was attributed to all three, but in the next verse, the pre-eminence of the chief personage is made clear.

"In the tent door ... behind him (the Lord) ..." Sarah was eavesdropping, the privilege of good wives in all generations! Little could she have anticipated that she would be exposed.