Can you tell me the story of how Sai Baba cured Amir Shakkar's rheumatism?

Certainly. Amir Shakkar was suffering from rheumatism and came to Sai Baba seeking deliverance from his sorrow. As detailed in Chapter 22, Baba's unique instruction was for Amir to reside steadily in the Chavadi. This place was old, dilapidated, and extremely uncomfortable, with dampness, cold, and various creatures. Despite the hardships, Amir stayed there for nine months based on his internal faith in Baba's word. This prolonged stay, which was externally like an imprisonment but internally was firm companionship with Sai, served as the cure for his affliction.