21.

"Father, yesterday the whole day I suffered from a serious headache. I prayed and prayed to You to cure me, but You did not listen to my prayer."

"Son, I am sorry. But son, you will be happy to know that I have spent the whole of yesterday in curing your malignant cancer, Doubt, which I have discovered in your mind. An aspirin can take care of your headache, but I am the only one who can take care of your mind."