What is the foundational belief in Aryavarta concerning spiritual salvation and the role of a Guru?

According to the preface of the Shri Sai Satcharita, there is a firm and ancient belief in Aryavarta that salvation is not possible without the grace of a Sadguru. This principle is not new; it has existed since Vedic times and is supported by Vedic scriptures. The text emphasizes that the form of the Sadguru can vary greatly—they can be a saint, a book, a family member, or even a friend. Chapter 0 explains that understanding how to serve them and receive their grace is a central aspect of the spiritual path.