What does the author say at the beginning of Chapter 21 about the qualities of a good narration and an attentive listener?

At the very beginning of Chapter 21, the author reflects on the dynamic between a speaker and a listener when recounting sacred stories. He posits that a speaker's words are essentially wasted if the listener is not deeply moved. The measure of a successful narration, according to this chapter, is its ability to evoke a physical and emotional response. The text specifically mentions that if the listener "does not sway upon hearing them" and "the hair on the body does not stand on end," the words have "gone in vain." It further describes narrations as "futile" if listeners are not delighted, if their throats do not "choke up with emotion," and if "tears of love and joy do not flow from the eyes."