What is the 'Satya-Sai vow' mentioned in the text and how did it originate?

According to the narrative in Chapter 13, the 'Satya-Sai vow' was a tradition started by the grateful Patil after he was miraculously cured of his disease. Just as people would vow to perform a Satyanarayan ritual to overcome a crisis, the Patil began performing this new vow. It involved reading the three chapters about Sainath from the modern 'Bhaktalilamrut' written by Das Ganu. The Patil would perform this vow regularly on Thursdays, seeing no difference between Narayan and Sai. This practice, which brought him boundless happiness and peace, became a custom in his village, showing how personal devotion can establish new traditions of faith.