Can you explain the analogy about the River Ganges in Chapter 47?

Chapter 47 uses a powerful analogy involving the River Bhagirathi, also known as the Ganges. The text explains that while the river washes the feet of the world and purifies others, it becomes soiled itself from the accumulated sins it washes away. To achieve its own purification and deliverance from these sins, the river desires the dust from the feet of saints and wishes for them to bathe within its waters. This analogy, presented in Chapter 47, serves to illustrate the supreme purifying power of saints like Sai, suggesting that their holiness is so great that even a sacred entity like the Ganges seeks their presence for its own cleansing.