In "The Wife of Bath's Tale", what information does the old woman share with the knight?
The knight in The Wife of Bath's Tale had committed a crime, but instead of being executed, he was given one year to live. In this year, he was tasked with finding an answer to the question "what do mortal women want most?". If his answer before the court was satisfactory, he would be allowed to live, and if not, he would be killed.
The knight spends most of the year seeking out women and hearing their opinions on the question, but it becomes clear that there is no consensus. Shortly before the year is up, he encounters the old woman, under supernatural circumstances, who tells him that old people "know many things".
She then tells him the answer to the question; that women most desire to have control over the men in their lives. This turns out to be an acceptable answer, and the knight's life is spared.
As a price for her help, the old woman demands that the knight marry her; he was no choice but to accept. He is miserable at the thought of this marriage, because she is old, ugly, and of common birth, but she educates him further;
But he who has nothing, nor covets things, is rich, albeit you count him as only a serving-lad.
This is practically a Buddhist passage; the old woman states that "low birth" has no bearing on one's goodness, ugliness is a guarantee of chastity, and that the knight's unhappiness is born merely of unfulfilled desires, and it is these desires which are the true source of that unhappiness. She reminds the knight of the examples set by Christ, of poverty and kindness, and reminds him that it would do him well to follow such an example.