In the Wife of Bath's tale a young man must set out on a journey in order to find out what women truly want. After his travels, he comes to the conclusion that:
A woman wants the self-same sovereignty
over her husband as over her lover,
and master him; he must not be above her.
However, once he finds this out and that he's correct, he needs to agree to marry the old woman who has posed the question. It is through this test that he discovers whether he can live with what he has found out or not.
Eventually, he offers her the mastery and she says:
Kiss me...No quarrels! On my oath
And word of honor, you shall find me both,
That is, both fair and faithful as a wife;
May I go howling mad and take my life
Unless I prove to be as good and true
As ever wife was since the world was new!
By allowing her to make the decision, the knight is offering her the power.