Can you tell me about the teachings of Saint Kabir and how they relate to the concept of Guru service discussed in the book's preface?

The preface to the Shri Sai Satcharita does not mention Saint Kabir or his specific teachings. However, it does provide a deep exploration of the principle of Guru service. The author, Balkrishna Vishwanath Dev, explains that while writing biographies of great individuals is a form of worldly service, it is limited and does not yield eternal spiritual fruits. As detailed in the preface (Chapter 0), a more spiritually fruitful service is writing the biographies of saints. The text further identifies the most certain and beneficial service as writing the biography of one's own Sadguru, studying it, and encouraging other devotees to do the same.