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

Chapter 47 employs a beautiful metaphor involving the River Bhagirathi, also known as the Ganges. The text posits that while the river washes the feet of the world and cleanses others' sins, it becomes soiled herself in the process. To wash away her own accumulated impurities, the river "desires the dust from the feet of saints." This metaphor highlights the supreme purifying power of saints like Sai Baba, suggesting that their holiness is so profound that even a sacred entity like the Ganges seeks their presence for its own deliverance from sin.