Can you explain the analogy involving the River Bhagirathi (Ganges) that is mentioned in Chapter 47?

In Chapter 47, a powerful analogy is used featuring the River Bhagirathi, or the Ganges, to highlight the immense purifying power of saints like Sai Baba. The chapter explains that while the Ganges cleanses the sins of the world, she becomes soiled herself from the accumulation of these impurities. To wash away her own collected sins, the river desires the dust from the feet of saints. This metaphor beautifully illustrates that the holiness of a true saint is so profound that it can purify even the ultimate purifier. This imagery is used to establish the supreme spiritual stature of Sai Baba, who is referred to as the "crown jewel among such saints," possessing a grace that transcends all else.