What was so special about the way Sai Baba spoke to Kaka Mahajani's friend that made him change his mind?

The magical power in Sai Baba's speech is detailed in Chapter 35. When the skeptical friend set foot in the mosque, Baba called out to him. It wasn't merely the words, "Why have you come in this manner?", but the exact tone and vocal style that astonished the man. He was amazed because it was a perfect imitation of his deceased father's voice, a voice he thought he would never hear again. Hearing speech as if from his father's own mouth caused the friend to melt inside, forget his prior convictions against bowing, and immediately bow his head at Baba's feet.