Could you explain the analogy about the River Ganges that is mentioned in Chapter 47?

In Chapter 47, a powerful analogy is used involving the River Bhagirathi, also known as the Ganges. The text explains that while the river purifies the world by washing away sins, it becomes soiled by the accumulated impurities. To achieve its own purification, the Ganges desires the dust from the feet of saints. As Chapter 47 illustrates, the river wonders when saints will come to bathe in its waters, knowing that this is the only way to find deliverance from its own sins. This metaphor powerfully illustrates the supreme purifying power of saints like Sai, whose holiness is sought even by sacred entities for their own cleansing.