Much misunderstanding surrounds the law in this week’s sidra that says lo yavo mamzer bik’hal HaShem – “A mamzer shall not enter the congregation of the Lord” (Deut. 23:3).
The English translations call a mamzer a bastard, which wrongly gives the impression that the mamzer is a child born out of wedlock.
In Jewish law the term applies to the child of parents who could never marry each other, either because of adultery (where the union is between a married woman and a man other than her husband) or incest. The child born to parents who were not but could legally have been married to each other is not a mamzer.
A second misapprehension applies to the words “shall not enter the congregation of the Lord”. The phrase does not imply that the child is not Jewish, or that if a male he could not be counted towards a minyan, or that he was debarred from holding communal office.
A mamzer’s only (though serious) impediment is that he or she may not marry a non-mamzer.
Obviously the child is suffering for the sins of the parents, and the halachah uses every possible leniency in applying the law, but prevention is better than cure, and couples who think of breaking the law should clearly think again.