2 Samuel 13:21

David … was very wroth. The legal punishment for Amnon's crime was "the being cut off in the sight of the people" (Le 2 Samuel 20:17 ). But how could David, who had himself committed crimes for which death was the appointed penalty, carry out the law against his firstborn for following his example? Still, he might have done more than merely give Amnon words of reproof. Eli had done as much, and been punished with the death of his sons for his neglect of duty ( 1 Samuel 2:34 ). The sin of David's son had been even more heartless than theirs; and could David hope to escape the like penalty? It would have been wise to have given proof that his repentance included the suppression of the crime to which his previous conduct had given encouragement. But David was a man whose conduct was generally governed by his feelings. He was a creature of warm and often generous impulse, but his character lacked the steadiness of thoughtful and consistent purpose.