Once a master was called to heal a sick child with a few words of prayer. A skeptic in the crowd observed it all and expressed doubts about such a superficial way of healing. The master turned to him and said, "You know nothing of these matters; you are an ignorant fool!" The skeptic became very upset. He turned red and shook with anger. Before he could gather himself to reply, however, the master spoke again, asking, "When one word has the power to make you hot and angry, why should not another word have the power to heal?"
Goldstein, Joseph and Kornfield, Jack. The Path of Insight Meditation (Shambhala Pocket Library) (pp. 13-14). Shambhala. Kindle Edition.
I have read several books by Kornfield. He is always enriching.