Can you explain the analogy of the River Ganges that is used at the start of Chapter 47?

Chapter 47 employs a powerful analogy involving the River Bhagirathi, or Ganges, to illustrate the purifying power of saints. The text posits that the river, in the process of washing away the world's impurities, becomes soiled herself. To cleanse herself of these accumulated sins, she yearns for the touch of saints. As described in Chapter 47, the river wonders, "When will the feet of saints touch me? When will they come to bathe within me?" This imagery powerfully conveys the idea that saints like Sai possess a purifying essence so great that even a sacred entity like the Ganges desires their presence for its own deliverance and purification.