Second, by the expression " commits adultery against her. "
Jesus introduced a view that was not recognized in the rabbinic courts,
the concept of a husband's committing adultery against his wife.

Explains The Expositor's Bible Commentary:
In rabbinic judaism a woman by infidelity could commit adultery against her husband; and a man,
by haveing sexual relation's with another man's wife, could commit adultery against him.
But a man could never commit adultery against his wife no matter what he did.

Jesus , by putting the husband under the same moral obligation as the wife,
raised the status and dignity of women.