2 Samuel 3:21-25

Abner said to David, “Let me set out and go and gather all Israel to my lord the king, so that they may make a covenant with you, and that you may be king over all that your soul desires.” So David let Abner go, and he went in peace.

And behold, the servants of David and Joab came from a raid and brought a large amount of plunder with them; but Abner was not with David in Hebron, since he had let him go, and he had gone in peace.

When Joab and all the army that was with him arrived, they informed Joab, saying, “Abner the son of Ner came to the king, and he has let him go on his way, and he has gone in peace.”

Then Joab came to the king and said, “What have you done? Behold, Abner came to you; why then have you let him go, so that he is already gone?

You know Abner the son of Ner, that he came to gain your confidence, and to learn of your going out and coming in and to find out everything that you are doing.” Joab Murders Abner