American Standard Version (ASV):
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.
King James Version (KJV):
And he said, I will certainly return unto thee according to the time of life; and, lo, Sarah thy wife shall have a son. And Sarah heard [it] in the tent door, which [was] behind him.