2 Samuel 13:3-5

3But Amnon had a friend, whose name was Jonadab, the son of Shimeah, David’s brother: and Jonadab was a very subtle man.

4And he said unto him, Why, O son of the king, art thou thus lean from day to day? wilt thou not tell me? And Amnon said unto him, I love Tamar, my brother Absalom’s sister.

5And Jonadab said unto him, Lay thee down on thy bed, and feign thyself sick: and when thy father cometh to see thee, say unto him, Let my sister Tamar come, I pray thee, and give me bread to eat, and dress the food in my sight, that I may see it, and eat it from her hand.