Can you explain the protocol for departing from Shirdi and how Udi is involved?

According to Chapter 35, departing from Shirdi requires Sai Baba's explicit permission, as transgressing his command can lead to dreadful interruptions and remorse on one's journey. Baba himself stated, "Without my wish, who will leave the doorstep?" The process of receiving this permission is deeply connected to the Udi. After bowing to Baba to ask for leave, the devotee is given a blessing along with the Udi Prasad. This act of receiving the Udi is described as the very sign of permission to leave, ensuring a safe and blessed departure under Sai's protection.