Can you explain the metaphor of the River Bhagirathi (Ganges) as it is described in Chapter 47?

In Chapter 47, the River Bhagirathi, or Ganges, is used in a powerful metaphor to illustrate the purifying power of saints. The text explains that while the river washes away the sins of the world, she becomes soiled with these accumulated impurities. To cleanse herself, she desires the dust from the feet of saints, knowing that without their touch, there is no deliverance from her own sins. This metaphor, found within Chapter 47, highlights the supreme spiritual status of saints like Sai, suggesting their purifying ability surpasses even that of the holy river itself.