What is the logic behind this? If the Kidushin of an Eved or Nochri can
never take effect with anyone, then on the contrary, the child should
certainly be a Mamzer!
(a) The RASHBA answers that the reason a child becomes a Mamzer is because
of the severity of the Isur involved with his conception. That severity is
expressed by the fact that the union between the mother and father could not
make Kidushin take effect. That is, the Isur is so severe that Kidushin
cannot exist in such a union.
In the case of a woman who is Asur to a man because of an Isur Ervah, since
she (and he) could marry others and have Kidushin take effect, but they
cannot marry each other, this shows that there is a very strong Isur between
them. It is the strength of the Isur that prevents Kidushin from taking
effect. However, in the case of an Eved or a Nochri, the fact that he cannot
make Kidushin with the Jewess with whom he had relations does not show
anything about the strength of the Isur, because an Eved and a Nochri cannot
make Kidushin with *anyone*. The reason they cannot make Kidushin with
anyone is because the Torah did not give them the ability to make Kidushin
in the first place. It has nothing to do with the Isur of the union between
him and a Jewess. Hence, the child is not a Mamzer.
RAV ELCHANAN WASSERMAN (in Kovetz He'oros 37:2) asks that according to the
explanation of the Rashba, how could the Gemara use this logic to legitimize
the child of an Eved or Nochri who had relations with a *married* Jewess (an
"Eshes Ish")? We know that the Isur of "Eshes Ish" is a strong Isur from the
fact that she cannot make Kidushin with even someone who is able to make
Kidushin (such as a normal Jewish man). Thus, even if she has relations with
an Eved or Nochri, we should say that the child should be a Mamzer!
Rav Elchanan answers that even though an Eshes Ish cannot make Kidushin with
any other man, since she could not make Kidushin with an Eved or Nochri
*even when she is not an Eshes Ish*, the fact that she is an Eshes Ish and
is unable to make Kidushin with anyone else does not affect the child.
This is difficult to understand, though, because the Rashba says that the
ability of Kidushin to take effect is only a *sign* of the strength of the
Isur. Accordingly, it should make no difference is she cannot make Kidushin
with an Eved because he is never fit for Kidushin. As far as the strength of
the Isur is concerned, we see from the fact that this Eshes Ish cannot
effect Kidushin with anyone that the Isur is very strong! What difference
does it make if Kidushin cannot be effected with an Eved? The child should
still be a Mamzer.
Another answer may be suggested to the original question of Rav Elchanan.
Even though an Eshes Ish has a very strong Isur to any other Jew,
nevertheless, the Isur to an Eved or Nochri is different, because the act of
Bi'ah with an Eved or Nochri is less severe (TOSFOS, Kesuvos 3b). Thus, an
Eved living with an Eshes Ish is a less severe Isur, and therefore we have
no proof for the strength of the Isur from the fact that she cannot make
Kidushin with any other Jew.
(b) The RAMBAN and RITVA cite RAV HAI GAON who had a different Girsa in the
Gemara. The text of his Gemara reads not that an Eved and Nochri cannot make
Kidushin, but that in the case of "an Eved and Nochri, the child's lineage
does not follow him (the father)," but rather it follows the Yichus of the
mother. That is why the child is not a Mamzer. The father cannot affect the
status of the child at all, even to give him a disqualifying trait, since
the lineage of the child is not traced at all to the father who is a Nochri
(as the Gemara says earlier on 17a).
They add that even though our Girsa is different, our Gemara might mean the
same thing. When our Gemara says that the Kidushin of an Eved and Nochri
does not take effect at all, it means that the father cannot affect the
status of the child because the child is not considered to be related to the
father, just like the Jewess with whom he had relations cannot be related to
the father (since Kidushin cannot take effect).