'When one obtains bliss (in oneself), then one performs duties. One who does not obtain bliss, does not perform duties. Only he who obtains bliss, performs duties. This bliss, however, we must desire to understand.' 'Sir, I desire to understand it.'

In plain words: A person does their duties only when they find joy within. Without that joy, a person does not act. So we must learn about this joy. Narada says he wants to learn it.