Have you ever had anyone give you advice that was not good, that was maybe even sinful, or that was not wise, and that did not turn out well? It is nice to have advice from family and friends, and help making decisions sometimes, but you have to be careful in taking people's advice to make sure that it is in your best interest. Have you ever had an advisor who turned on you, maybe even stabbed you in the back for who knows what reason? Maybe that advisor had his/her own agenda, was self serving, had some thing that person wanted for him/herself, or at least not in your best interest.
This happened in the case of Amnon and Tabar in David's family in the Old Testament. Amnon had a friend who was not really a friend, who was his first first cousin. His name was Jonadab, and he was David's brother's son. The description of Jonadab was the same as the serpent in the Garden of Eden. He was subtle, a conniver, a person who would talk you into things that you shouldn't go along with. He was a person who was on the wrong side of right and wrong.
Jonadab asked Amnon, his friend and cousin, what was wrong with him. Then Amnon confided in Jonadab that he loved Tamar and wanted her. So Jonadab advised Amnon to play sick in order to get Tamar to come to him. Then when Tamar came, and Amnon got her into his bed chamber, he was stronger than she was, so he grabbed her and raped her. That advise had a very bad ending that made David angry, and set Absalom Tabar's brother to plotting Amnon's murder which took place two years later. After the whole thing went bad, and Absalom had killed Amnon, Jonadab told David that Absalom determined to kill Amnon from the day that Amnon had raped his sister Tamar. Jonadab knew that his advice had caused this whole sordid situation, but he made no efforts to protect anyone from evil or harm, but after it was over with and Amnon was dead, then Jonadab told David this is why it happened, just as if he had no part in what took place. Jonadab had caused a lot of grief to David's family, caused them to be in mourning. They all including David, his servants, and his sons wept very sore. David mourned for his son, Amnon every day. Amnon had guilt over this action, but none of them wanted him to be killed. Then Absalom fled and was gone three years after which he returned to cause more grief to David's family, which eventually caused his own murder, and more grief for David. Bad advisers are often trouble makers as well.