Why did Sai Baba instruct Amir Shakkar, who was suffering from rheumatism, to stay in the dilapidated and uncomfortable Chavadi?

According to Chapter 22, Amir Shakkar was afflicted by rheumatism and prayed to Sai Baba for a remedy. Baba's instruction was for him to stay steadily in the Chavadi. This was a profound test of faith, as the Chavadi was an old, dilapidated, and extremely uncomfortable place, filled with dampness, holes, and even scorpions. Despite the external conditions being contrary to healing, Amir was told to accept Baba's word as his medicine. He stayed for nine months, and the text suggests that his internal faith was the key element in this arrangement, as the company of Sai was considered the 'Great Prasad' that transcended the physical squalor.