How did Sai Baba manage to make a man who was against idol worship bow down to him?

The incident is detailed in Chapter 35. The man, a friend of Kaka Mahajani, was a staunch devotee of the formless and had resolved not to bow. When he arrived at the mosque, Sai Baba saw him from a distance and called out, 'Why have you come in this manner?' The power was not in the words themselves, but in the delivery. As Chapter 35 explains, the tone and vocal style were a 'perfect imitation' of the friend's deceased father. This incredibly personal and unexpected event astonished the man, who recognized the voice as familiar. The 'magic power' in that speech made him forget his intellectual convictions and he instinctively bowed at Baba's feet.