David is severely beaten by his father when he wishes that he had another hand.
In David’s society, everyone is devoutly religious and they consider everyone to be made in the image of God. Anyone not made in the image of God is an abomination and is cast off and destroyed. When David gets a splinter and absentmindedly wishes that he had an extra hand one day, his tyrannically pious father loses it.
'You do know -- and yet, knowing this, you deliberately wished yourself a Mutant. That is a terrible thing, an outrageous thing. You, my son, committing blasphemy, and before his parents!' (Ch. 3)
David’s father is upset because, in front of farm hands, he thinks that David called upon the Devil to give him a third hand. David did no such thing. He simply said if he had another hand he could have held onto the tie better. It was an innocent pronouncement most people would make. However, in a society like David’s where everyone is so afraid, David’s father is acting out of fear. He doesn’t want to get a reputation of being soft. This is why he is so hard on David, and immediately insists that he pray.
Even given that, it was not necessary for David’s father to be so harsh. He did not need to beat David as badly as he did for his childish mistake. David’s father has a position of importance in the community, and is a cruel tyrant.
This incident foreshadows when David has to leave, when it is discovered that he really is a deviant because he is telepathic. David’s father beats him later, when he finds out that he has been hanging out with Sophie, who is a deviant. He is just as annoyed by this, because it is damaging to his reputation, especially since the inspector came to his house to question David about it. Deviance is not acceptable, and his father is not forvgiving.