[A. Pole]

Monogamy was introduced by the Church.

It became customary around the time of Ezra.

But it became a rule among the Jews about 1000 years after birth of Christ.

[Salman]

But it became a rule among the Jews about 1000 years after birth of Christ.

In terms of enforcement, yes. But monogamy was always the Biblical norm, all the way back. Only one Eve in the garden.

In fact the rabbinical ruling was a response to people breaking the custom (within the letter of the law).