2 Samuel 3:23-25

23When Joab and all the soldiers with him arrived, he was told that Abner son of Ner had come to the king and that the king had sent him away and that he had gone in peace. 24So Joab went to the king and said, “What have you done? Look, Abner came to you. Why did you let him go? Now he is gone! 25You know Abner son of Ner; he came to deceive you and observe your movements and find out everything you are doing.”