Joab and his brother Abishai killed Abner because he had put their brother Asahel to death in the battle at Gibeon.

David then ordered Joab and all the people who were with him, “Tear your clothes, put on sackcloth, and mourn over Abner.” And King David walked behind the funeral procession.

when the person told me, ‘Look, Saul is dead,’ he thought he was a bearer of good news, but I seized him and put him to death at Ziklag. That was my reward to him for his news!

He also defeated the Moabites, and after making them lie down on the ground, he measured them off with a cord. He measured every two cord lengths of those to be put to death and one length of those to be kept alive. So the Moabites became David’s subjects and brought tribute.

In the letter he wrote:

Put Uriah at the front of the fiercest fighting, then withdraw from him so that he is struck down and dies.

When Joab was besieging the city, he put Uriah in the place where he knew the best enemy soldiers were.

He removed the people who were in the city and put them to work with saws, iron picks, and iron axes, and to labor at brickmaking. He did the same to all the Ammonite cities. Then he and all his troops returned to Jerusalem.

Tamar put ashes on her head and tore the long-sleeved garment she was wearing. She put her hand on her head and went away crying out.

So Joab sent someone to Tekoa to bring a clever woman from there. He told her, “Pretend to be in mourning: dress in mourning clothes and don’t put on any oil. Act like a woman who has been mourning for the dead for a long time.

Now the whole clan has risen up against your servant and said, ‘Hand over the one who killed his brother so we may put him to death for the life of the brother he murdered. We will destroy the heir!’ They would extinguish my one remaining ember by not preserving my husband’s name or posterity on earth.”

The king asked, “Did Joab put you up to all this?”

The woman answered. “As you live, my lord the king, no one can turn to the right or left from all my lord the king says. Yes, your servant Joab is the one who gave orders to me; he told your servant exactly what to say.

Abishai son of Zeruiah asked, “Shouldn’t Shimei be put to death for this, because he cursed the Lord’s anointed?”

The Gibeonites said to him, “We are not asking for money from Saul or his family, and we cannot put anyone to death in Israel.”

“Whatever you say, I will do for you,” he said.

He was the most honored of the Thirty, but he did not become one of the Three. David put him in charge of his bodyguard.