Based on Chapter 16, what is the fundamental requirement for a disciple to receive the Guru's grace and knowledge?

The fundamental requirement for a disciple, as detailed in Chapter 16 of the Sai Satcharitra, is absolute and humble surrender to the Sadguru. The text makes it clear that other means will fail and that even a slight use of 'cleverness' or ego in service can cause problems for the seeker. The chapter explains that a disciple should simply surrender themselves, as they are often unaware of their own faults and spiritual pitfalls. It is the Guru who, seeing this surrender, provides the remedy and guidance. By serving with faith, the disciple can attain union with Brahman. Therefore, firm faith at the Guru's feet and complete surrender are presented as the most essential qualities for receiving His ultimate grace and knowledge.