What specific event caused Kaka Mahajani's friend to break his promise and bow to Sai Baba?

Kaka Mahajani's friend, who was initially a doubter, had a profound change of heart due to a very personal experience. According to Chapter 35, he had firmly resolved not to bow his head. But as he set foot on the step of the mosque, Sai Baba called out to him. The friend was immediately astonished because Baba's tone and way of speaking were an exact match to his own deceased father's. Hearing a voice so familiar and cherished, as if from his father's own mouth, made the friend melt inside and completely forget his prior resolution, leading him to bow at Baba's feet.