Chapter 47 uses an analogy involving the River Ganges. What is this analogy and what point is it trying to make?

In Chapter 47, a powerful analogy is used to illustrate the supreme purity of saints like Sai Baba. The text explains that the River Bhagirathi (Ganges) becomes soiled by washing away the sins of the world. To cleanse herself of these accumulated impurities, she desires the dust from the feet of saints. The chapter states that the river knows there is no other way to achieve deliverance from her sins. This analogy, presented in Chapter 47, serves to underscore the immense spiritual power and holiness of a Sadguru. It suggests that their purity is so profound that even a sacred entity like the Ganges, which purifies others, must seek them out for its own purification, thereby emphasizing the unparalleled grace of a true saint.