Gershom of Mayyence
German legal authority created famous ban against divorcing a wife against her will.
Reprinted from The Jewish Religion: A Companion, published by Oxford University Press.
Gershom of Mayyence was a prominent German Jewish leader and legal authority (960-1028), also known as Rabbenu (Our Master) Gershom and as "Light of the Exile." The great French commentator Rashi remarked that all French and German scholars are the disciples of Gershom's disciples.
Gershom considers in his writings some of the problems that arose for Jews in Christian society. He was asked whether a kohen, a priest, who had been converted to Christianity but later returned to the Jewish fold can enjoy the priestly privileges of being called up first to the reading of the Torah and reciting the priestly blessing in the synagogue. Gershom's reply is in the affirmative. Apostates must be encouraged to return and welcomed, not disbarred from exercising the rights they previously enjoyed.
There is an ancient report to the effect that a son of Gershom was forcibly converted to Christianity and yet Gershom mourned for him. The meaning is that Gershom mourned for the son when the son died, since he was still his son. But, at a later date, the report was misunderstood to mean that Gershom mourned for his son when he heard of the son's apostasy as if the son had died. This led in some circles to the bizarre practice of a family observing the rites of mourning when a member of the family became a convert to Christianity, even while the apostate was still alive.
There are a number of communal enactments attributed to Gershom, although some scholars believe that these were only fathered on him later. In any event each of these is known as the herem (ban) of Rabbenu Gershom. One forbids a postman opening a letter to read its contents. But the two most famous of the bans are that on a man having more than one wife at the same time and that on divorcing a wife against her will. The latter was introduced to prevent a man who wished to take a second wife divorcing his first wife whether or not she agreed to the divorce.
The ban of Rabbenu Gershom was only binding on Ashkenazi Jews since Gershom, as an Ashkenazi leader, had no power to impose his rulings upon Sephardi Jews.