In the previous section we learned in the Mishnah that the rapist, who forces himself upon a young woman, "shoteh be'atzitzo" - he must drink from the cup he himself poured. He is obligated to marry her and to remain married to her, provided that she and her father want this.
How "shoteh be'atzitzo" plays out in practice:
Our Mishnah seeks to clarify how far this obligation extends, and in what circumstances a man has no way out of it:
"Afilu chigeret" - even if she is lame in her leg.
"Afilu suma" - even if she is blind.
"Afilu mukas shechin" - even if she is afflicted with boils and severe skin diseases.
In all of these cases he is obligated to marry her, and these defects are not enough to release him from the obligation.
If something forbidden is found in her:
However, if a matter of forbidden relations is found in her, he may no longer keep her as his wife. There are two situations here:
"Nimtza bah devar ervah" - that she committed adultery after he married her.
"O she'einah re'uyah lavo b'Yisrael" - that she is not permitted to enter the congregation of Israel, such as a mamzeres or an Egyptian convert, who is forbidden to him by Torah law.
In both of these cases "eino rashai lekayemah" - he may not keep her with him as his wife, since this obligation does not have the power to permit him to transgress a Torah law.
The source for this is in the wording of the verse: "velo tihyeh l'ishah" - stated in the passage dealing with the rapist, and from here we learn that she must be "a woman who is fit for him," that is, a woman who is permitted to him. But if she is forbidden to him by Torah law, he cannot remain married to her, and he has no obligation whatsoever to marry her under these circumstances.
In summary: In this Mishnah we learned the scope of the principle "shoteh be'atzitzo": the rapist marries the young woman even if she is lame, blind, or afflicted with boils. But when a matter of forbidden relations is found in her, or she is not fit to enter the congregation of Israel, he may not keep her as his wife, for the verse says "velo tihyeh l'ishah" - a woman who is fit for him.