Jonadab said to Amnon, “You are the king's son, yet day after day I see you looking sad. What's the matter?” “I'm in love with Tamar, the sister of my half brother Absalom,” he answered.
Jonadab said to him, “Pretend that you are sick and go to bed. When your father comes to see you, say to him, ‘Please ask my sister Tamar to come and feed me. I want her to fix the food here where I can see her, and then serve it to me herself.’”
My people, were you ashamed because you did these disgusting things? No, you were not ashamed at all; you don't even know how to blush! And so you will fall as others have fallen; when I punish you, that will be the end of you. I, the Lord, have spoken.
If a man marries his sister or half sister, they shall be publicly disgraced and driven out of the community. He has had intercourse with his sister and must suffer the consequences.