Based on the provided text, what is the connection between receiving Udi and getting Sai Baba's permission to leave?

The source material from Chapter 35 establishes a direct and crucial connection between receiving Udi and obtaining Sai Baba's permission to leave Shirdi. It is explicitly stated that 'the blessing along with the Udi is the permission to leave.' This is not merely a parting gift but the formal sanction for departure. The text emphasizes that no one can come to or leave Shirdi without Sai's will. Thus, the act of receiving the Udi Prasad signifies that Sai's heart is pleased and he has granted his consent for the journey, protecting the devotee from the remorse and obstacles that come from leaving by one's own will.