How does the sacred ash, or Udi, demonstrate Sai Baba's power and grace according to the experiences shared in the source material?

The provided sections of Chapter 35 highlight the immense power and grace of Sai Baba as manifested through his Udi. It is described as a 'Prasad' and a blessing that carries Sai's influence. One powerful example is its role as the definitive permission to leave Shirdi, without which a devotee's journey could be fraught with obstacles. Another experience demonstrates its healing and protective qualities. A gentleman from Bandra, tormented by nightly nightmares of his deceased father, found immediate relief after a devotee advised him. By applying the Udi to his head, placing it under his pillow, and keeping faith in Sai, his bad dreams were completely erased. This illustrates that the Udi's 'natural tendency' is to remove trouble when used with devotion.