Jamieson, Fausset and Brown on 2 Samuel 18:11-12

11-12. Joab said unto the man that told him, ... I would have given thee ten shekels of silver, and a girdle--that is, would have raised him from the ranks to the status of a commissioned officer. Besides a sum of money, a girdle, curiously and richly wrought, was among the ancient Hebrews a mark of honor, and sometimes bestowed as a reward of military merit. This soldier, however, who may be taken as a fair sample of David's faithful subjects, had so great a respect for the king's wishes, that no prospect of reward would have tempted him to lay violent hands on Absalom. But Joab's stern sense of public duty, which satisfied him that there could be neither safety to the king, nor peace to the kingdom, nor security to him and other loyal subjects, so long as that turbulent prince lived, overcame his sensibilities, and looking upon the charge given to the generals as more befitting a parent than a prince, he ventured to disobey it.

2Sa 18:14-32. He Is Slain by Joab.