Why Scripture Says Sarah Had No Child At All

"Now Sarai was barren" (Genesis 11:30). Rabbah bar Avuha said: Sarah was a woman incapable of bearing [an ailonit], for it is stated, "Now Sarai was barren; she had no child" she did not even have a womb [literally, a "house of the child," the place where a child is formed]. Rabbi Ami said: Abraham and Sarah were of indeterminate sex [tumtumim], as it is written, "Look to Abraham your father and to Sarah who bore you. Look to the rock from which you were hewn, and to the quarry from which you were dug" (Isaiah 51:1-2) [the language of "hewing" and "digging" implying that their generative capacity had to be opened up].