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

In Chapter 47, the sacred River Bhagirathi, or Ganges, is used in an analogy to demonstrate the supreme purifying power of saints. The text explains that the river, by washing the feet of the world, becomes soiled with impurities. To cleanse herself of these accumulated sins, the river 'desires the dust from the feet of saints.' As the chapter puts it, the river knows for certain that without the touch of a saint's feet, there is no deliverance from her own sins. This metaphor from Chapter 47 powerfully conveys that saints like Sai Baba possess a level of purity so profound that even a holy entity like the Ganges seeks them out for its own purification.