2 Samuel 13:1-4

Now it was after this that Absalom the son of David had a beautiful sister whose name was Tamar, and Amnon the son of David was in love with her.

But Amnon was so frustrated on account of his sister Tamar that he made himself ill, for she was a virgin, and it seemed too difficult to Amnon to do anything to her.

But Amnon had a friend whose name was Jonadab, the son of Shimeah, David’s brother; and Jonadab was a very clever man.

And he said to him, “Why are you, the king’s son, so depressed morning after morning? Will you not tell me?” So Amnon said to him, “I am in love with Tamar, the sister of my brother Absalom.”