(Bamidbar 5:298) "And if the woman had not been defiled and she be clean": What is the intent of this? From (Vayikra 20:10) "And a man who lives with another man's wife, etc.", we learn that only where there were witnesses (to her adultery) and she were forewarned that she is put to death. If there were witnesses, but she had not been forewarned, she is not liable to the death penalty. (I would think that) since she is not liable to the death penalty she is permitted to her husband; it is, therefore, written (Devarim 24:1) "If a man take a woman (as a wife) and cohabit with her … having found in her a thing of nakedness … he shall write her a scroll of divorce, etc." — whence we learn that she is forbidden to her husband.
Whence is derived (the halachah) in an instance of doubt as to whether or not she has been defiled? From "And the woman had not been defiled and she be clean." Now who defiled her that Scripture must cleanse her? We are being told, then, that since an evil name has gone out against her, she is forbidden to her husband. "and she be clean": clean to her husband, clean to the (suspected) cohabitor (i.e., if her husband divorced her or died, he may marry her), and clean vis-à-vis (the eating of) terumah. "then she shall be absolved": of the curses and of the oath. "and she will sow seed": If she were barren, she conceives.
These are the words of R. Yishmael. R. Akiva said to him: If so, all the barren ones will go astray (and secrete themselves) in order to conceive and the modest (barren) ones will lose out! What, rather, is the intent of "then she will be absolved and she will sow seed"? If she had borne only females, she will now bear males; if she had borne only one, she will now bear two; if she had borne swarthy ones, she will now bear fair ones; if she had borne short ones, she will now bear fair ones.
R. Shimon says: Would it enter your mind that she is rewarded for transgression (i.e., secreting herself)? Rather, because she had been forbidden (to her husband) for seed before (drinking), it is, therefore, written "and she will sow seed," i.e., she is now permitted for "seed." Variantly: "and she will sow seed" — to exclude (from drinking) an eilonith (a wombless woman) or one who is (otherwise) unfit to bear.